MDEV-15811 Fix and re-enable test galera.galera_pc_ignore_sb

* After killing one galera node with include/kill_galera,
  wait for cluster to shrink

* Remove unnecessary include/wait_until_connected_again.inc

xb_assign_undo_space_start(): Correctly pass the length of
the buffer, so that the file name will not be truncated.

dict_load_table_low(): When flagging an error, assign *table = NULL.
Failure to do so could cause a crash if an error was flagged when
accessing INFORMATION_SCHEMA.INNODB_SYS_TABLES.

MDEV-15948 Fix error "Lost connection to MySQL server..." in test gal…

While the test case crashes a MariaDB 10.2 debug build only,
let us apply the fix to the earliest applicable MariaDB series (10.0)
to avoid any data corruption on a table-rebuilding ALTER TABLE
using ALGORITHM=INPLACE.

innobase_create_key_defs(): Use altered_table->s->primary_key
when a new primary key is being created.

* Increased timeout counter in galera_wait_ready.inc

* Replaced useless include/wait_until_ready.inc after start_mysqld.inc
  in galera_st_*.inc with wait_condition on cluster size.

MDEV-15929 Fix lock wait timeout on `SELECT @@GLOBAL.WSREP_ON`

followup for a3c980b3

same change in Locked_tables_list::unlink_from_list(), otherwise
thd->locked_tables_list will keep pointers to a free'd TABLE if
prelocked under lock tables.

This fixes a crash in main.create_or_replace on debug Win builds
after bcb36ee2

do_stmt_close() is embedded-aware.

this fixes the failure of innodb.innodb_bug48024 --ps --embed

Test galera_sst_mysqldump often fails with error "2013: Lost connection
to MySQL server during query". The connection is lost after the test
restart one of the nodes. This happens because the server closes client
connections if it is joining a cluster through SST method mysqldump.
On unlucky runs of the test it is possible that mysqld is restarted,
and then mtr client is disconnected while it tries to determine if
galera is ready before going on with the test.
This patch rewrites galera_wait_ready.inc so that it is immune to
being disconnected.

MDEV-15456 Server crashes upon adding or dropping a partition in ALTER under LOCK TABLE after ER_SAME_NAME_PARTITION

ALTER TABLE ... ADD PARTITION modifies the open TABLE structure,
and sets table->need_reopen=1 to reset these modifications
in case of an error.

But under LOCK TABLES the table isn't get reopened, despite need_reopen.

Fixed by reopening need_reopen tables under LOCK TABLE.

bad merge

in a specially crafted invalid packet, one can get end_pos < pos here

disable online alter add primary key for innodb, if the
table is opened/locked more than once in the current connection

(see assert in ha_innobase::add_index())

test case

This patch fixes a lock wait timeout error on `SELECT @@GLOBAL.WSREP_ON`
in `wait_wsrep_ready.inc`:

```
--connection node_2
...
--source include/kill_galera.inc

--connection node_1
--source include/wait_until_connected_again.inc # This includes wait_wsrep_ready.inc

```

The problem is that on node_2, kill_galera.inc may return before
the node is killed. So node_1 may still see that node_1 is alive
and will attempt to sync wait when doing those `SELECT` statements.
But sync wait is doomed to fail given that node_1 is killed, hence
the lock wait timeout.
One possible fix is to disable wsrep_sync_wait before including
wait_until_connected_again.
However, it appears that including wait_until_connected_again is
not necessary at all in node_1, so this patch removes it altogether.

one cannot do keyread on spatial indexes.

Any expensive WHERE condition for a table-less query with
implicit aggregation was lost. As a result the used aggregate
functions were calculated over a non-empty set of rows even
in the case when the condition was false.

fil_crypt_rotate_pages
	If tablespace is marked as stopping stop also page rotation

fil_crypt_flush_space
	If tablespace is marked as stopping do not try to read
	page 0 and write it back.

Also clarify which --{no-,}default* options, must be first.

Sample output:
$  client/mysql --help
client/mysql  Ver 15.1 Distrib 5.5.59-MariaDB, for Linux (x86_64) using readline 5.1
Copyright (c) 2000, 2017, Oracle, MariaDB Corporation Ab and others.

Usage: client/mysql [OPTIONS] [database]

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf
The following groups are read: mysql client client-server client-mariadb
The following options may be given as the first argument:
--print-defaults          Print the program argument list and exit.
--no-defaults             Don't read default options from any option file.
The following specify which files/groups are read (specified before other options):
--defaults-file=#         Only read default options from the given file #.
--defaults-extra-file=#   Read this file after the global files are read.
--defaults-group-suffix=# Additionally read default groups with # appended as a suffix.

tests running from build directory:
TEST: print defaults ignored as not first
$ sql/mysqld  --no-defaults --print-defaults --lc-messages-dir=${PWD}/sql/share

TEST: no startup occurs as --print-defaults specified
$ sql/mysqld  --print-defaults --lc-messages-dir=${PWD}/sql/share
sql/mysqld would have been started with the following arguments:
--lc-messages-dir=/home/dan/repos/build-mariadb-5.5/sql/share

TEST: default args can't be anywhere
$ client/mysql --user=bob  --defaults-file=/etc/my.cnf
client/mysql: unknown variable 'defaults-file=/etc/my.cnf'
$ client/mysql --user=bob  --defaults-group-suffix=.group
client/mysql: unknown variable 'defaults-group-suffix=.group'

/etc/my.cnf:
[client-server.group]
socket=/var/lib/mysql-multi/group/mysqld.sock
user=bob

/etc/my.other.cnf:
socket=/var/lib/mysql-other/mysqld.sock

TEST: defaults file read and suffix also applied
$  client/mysql  --defaults-file=/etc/my.other.cnf  --defaults-group-suffix=.group
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql-other/mysqld.sock' (2)

TEST: defaults extra file
$ client/mysql  --defaults-extra-file=/etc/my.other.cnf  --defaults-group-suffix=.group
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql-other/mysqld.sock' (2)

Fixed typo on select that is executed only when something unexpected
happens.

MDEV-12632: Source and destination overlap in memcpy, encryption.innodb-discard-import-change fails in buildbot with valgrind

Use block->page.offset for checking page number.

Problem was that we did not delete explain information
when Galera must replay a query.

Could not find easily repeatable test case that would not
cause other problems.

CIFS does not like O_DIRECT flag (it is set successfully, but pread would
fail).

The fix is not to use O_DIRECT, there is not need for it.
posix_fadvise() was used already that should prevent buffer cache
pollution on Linux.

As recommended by documentation of posix_fadvise(), we'll also fsync()
tablespaces after a batch of writes.

System tablespace can be specified with absolute path, if innodb_data_home_dir
is empty.

This was not handled well  by mariabackup

1. In backup phase, empty innodb_data_home_dir variable from server was
not recognized. full paths were stored in backup-my.ini, even if
it stored all files locally. thus prepare phase would not find the system
tablespace files.

2. In copy-back phase, copy would not be done to the absolute destination
path, as path would be stripped with trim_dotslash

This patch fixes the above defects.

MDEV-12632: Source and destination overlap in memcpy, encryption.innodb-discard-import-change fails in buildbot with valgrind

Problem was that if tablespace was encrypted we try to copy
also page 0 from read buffer to write buffer that are in
that case the same memory area.

fil_iterate
	When tablespace is encrypted or compressed its
        first page (i.e. page 0) is not encrypted or
	compressed and there is no need to copy buffer.

Wait until rotation has ended and shutdown before grep to make sure
that dirty pages are on datafiles.

Return early if plugin is not built.

MDEV-15804 Fix and re-enable MTR test galera.pxc-421

MDEV-15808 Fix and re-enable test galera.galera_gra_log

This patch makes two changes:

* Remove unnecessary `set SESSION wsrep_sync_wait=0`.
  Disabling `wsrep_sync_wait` caused the test to fail occasionally,
  due to subsequent `SELECT`s observing stale values.

* Remove redundant `--source include/galera_wait_ready.inc`,
  `galera_wait_ready.inc` is already included in the above
  `wait_until_connected_again.inc`