When connecting to a master node, the client needs to try a different
master if the initially tried one is a secondary master node. This
statement wasn't implemented yet before this patch and therefore it was
good luck if the initally tried master was the primary one - and the
connection worked - or if it was a secondary master - and the client
got stuck in re-trying the same node forever. This patch makes NEO/go
usage with clusters of more than one master therefore much more stable.

After initial handshake a NEO node checks the identification of its peer
by sending the 'RequestIdentification' packet. In case the peer is a
secondary master it responds with 'NotPrimaryMaster'. Before this patch
'Dial' ignored the 'NotPrimaryMaster' packet and simply returned a
general error. Now - after this patch - 'Dial' returns an instance of
'proto.NotPrimaryMaster' (which implements 'Error').
This helps a caller to correctly handle the secondary-master-case, which
otherwise is impossible to differentiate from any other error
possibility.

When a client receives `NotPrimaryMaster` from a secondary master, the
situation is similar as when we receive an error: the other node tells,
don't connect with me, connect with someone else. Finally the peer
even closes the connection.

Due to this similarity in structure (& because it helps us later to
teach NEO/go to correctly handle `NotPrimaryMaster` with minimal
changes), we implement `Error` for `NotPrimaryMaster`.

In a NEO URI more than one master node can be specified, because a NEO
cluster may have more masters than one. But before this patch
'openClientByURL' always assumed that the given URL only specifies one
master. Now the host is split into potentially > 1 master nodes. It
therefore works now in the same way as the Python implementation [1].

[1] https://lab.nexedi.com/nexedi/neoppod/blob/342168cd/neo/client/zodburi.py#L64

Before this patch Client.URL didn't contain more than one master node.
This can be problematic in case we have a cluster with > 1 master nodes
and the printer master is a secondary master (which may be down). In
this case the user who trusts the "URL" attribute to connect to the
cluster won't succeed, because the primary master can't be reached.

Some NEO clusters have more than one master to gain a higher availability.
Before this patch NEO/go Node type only handled one master address. This
commit adjusts the node type and related bits so that it can support more than
one master node.

* master:
  go/neo: Expand user prefix in TLS key/cert paths
  go/neo/interal += xpath, xfilepath

This patch fixes a discrepancy between NEO/py and NEO/go: NEO/py expands
the '~' and the '~username' prefix in the file path of the TLS
certificate/key files [1]. This syntax is used in NEO/py SlapOS SR [2].
We need to fix this discrepancy in NEO/go in order to use TLS encryption
with NEO + WCFS.

[1] https://lab.nexedi.com/nexedi/neoppod/blob/7c539f0f/neo/lib/config.py#L149
and https://lab.nexedi.com/nexedi/neoppod/blob/fa63d856/neo/lib/app.py#L25-31

[2] https://lab.nexedi.com/nexedi/slapos/blob/397726e1/stack/erp5/instance-zodb-base.cfg.in#L18-20
and https://lab.nexedi.com/nexedi/slapos/blob/a8150a1a/software/neoppod/instance-neo-input-schema.json#L62

/reviewed-by @kirr
/reviewed-on !1

The xfilepath package supports resolving filepaths with a user prefix
to absolute paths: it converts '~' and '~username' to $HOME of user
(as it's done by for  instance bash). No builtin golang module supports this
functionality [1]. We need this functionality in order to imitate the
behaviour of NEO/py in NEO/go [2].

---

[1] https://stackoverflow.com/questions/47261719/how-can-i-resolve-a-relative-path-to-absolute-path-in-golang)
[2] nexedi/slapos!1307 (comment 17574)

/reviewed-by @kirr
/reviewed-on !1

* master:
  go/neo/t/neotest: Use python -c 'print ...' in a way that works on both py2 and py3
  go/neo/t/tzodb.py: Fix zhash for Python3

Without parenthesis it was failing on py3:

	(neo) (py3.venv) (g.env) kirr@deca:~/src/neo/src/lab.nexedi.com/kirr/neo/go/neo/t$ ./neotest info-local
	date:   Wed, 18 May 2022 11:05:50 +0300
	xnode:  kirr@deca.navytux.spb.ru (2401:5180:0:af::1 192.168.0.3 (+ 1·ipv4))
	uname:  Linux deca 5.10.0-13-amd64 #1 SMP Debian 5.10.106-1 (2022-03-17) x86_64 GNU/Linux
	cpu:    Intel(R) Core(TM) i7-7600U CPU @ 2.80GHz
	  File "<string>", line 1
	    print '%.2fGHz' % (400000 / 1E6)
	          ^
	SyntaxError: invalid syntax

On py3 dict.keys() returns iterator instead of list:

    $ ./tzodb.py zhash
    Traceback (most recent call last):
      File "/home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/neo/t/./tzodb.py", line 141, in <module>
        main()
      File "/home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/neo/t/./tzodb.py", line 138, in main
        zhash()
      File "/home/kirr/src/neo/src/lab.nexedi.com/kirr/neo/go/neo/t/./tzodb.py", line 59, in zhash
        optv, argv = getopt(sys.argv[2:], "h", ["help", "check=", "bench="] + hashRegistry.keys())
    TypeError: can only concatenate list (not "dict_keys") to list

* master:
  go/internal/xurl: New package (draft)

With xurl.ParseQuery being simpler analog of url.ParseQuery.
Simpler: It returns regular map instead of url.Values by not allowing duplicates.

Instead of requiring users to explicitly mark their tests as finished in
particular subject-to-deadlock places, tracetest was fixed to
unconditionally detect "extra sends" deadlocks automatically:

kirr/go123@3b19f68c

go get: upgraded github.com/fsnotify/fsnotify v1.4.10-0.20200417215612-7f4cf4dd2b52 => v1.5.1
go get: upgraded github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b => v1.0.0
go get: upgraded github.com/gwenn/gosqlite v0.0.0-20201008200117-82e079acf5b6 => v0.0.0-20211101095637-b18efb2e44c8
go get: upgraded github.com/gwenn/yacr v0.0.0-20200112083327-bbe82c1f4d60 => v0.0.0-20211101095056-492fb0c571bc
go get: upgraded github.com/kisielk/og-rek v1.1.0 => v1.2.0
go get: upgraded github.com/soheilhy/cmux v0.1.5-0.20210205191134-5ec6847320e5 => v0.1.5
go get: upgraded github.com/tinylib/msgp v1.1.5 => v1.1.6
go get: upgraded golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 => v0.0.0-20211111160137-58aab5ef257a
go get: upgraded golang.org/x/sys v0.0.0-20210301091718-77cc2087c03b => v0.0.0-20211111213525-f221eed1c01e
go get: upgraded golang.org/x/text v0.3.5 => v0.3.7
go get: upgraded lab.nexedi.com/kirr/go123 v0.0.0-20210128150852-c20e95f0f789 => v0.0.0-20210906140734-c9eb28d9e408

Highlights:

- og-rek brings support for pickle protocol 5
- go123  brings in support for Go1.17

* master:
  go/zodb/btree: Change V<op> family to also provide visited node key coverage on visit callback
  go/zodb/btree: Add KeyRange type
  go/zodb/btree: Introduce constants for min/max key value
  go/zodb/btree: tests: Don't forget to close storage
  go/zodb/btree: Cosmetics

WCFS needs to know key coverage for every visited node.

WARNING: this is API change.

KeyRange represents [lo,hi) key range. It simplifies working with ranges
of keys. We will use it in the next commit.

KeyRange originated in WCFS and was copied from there:

https://lab.nexedi.com/kirr/wendelin.core/blob/57be0126/wcfs/internal/xbtree/blib/keyrange.go

We were already using math.Min<Key> in one place, but the number of such
places is going to increase. -> Keep min/max definition in only one place.

NOTE: db was already being closed in the test's code.

* t+btree:
  .
  .
  .
  .
  .
  .
  .
  X Start reworking BTree to provide keycov on visit callback

Due to security concerns, go1.17, even though very reluctantly,
similarly to Python broke backward compatibility and stopped to treat ';'
as separator when parsing URL queries.

We still want to accept ';' as separator in credential part.
-> Work it around by replacing ';' -> to '&'.

See https://golang.org/doc/go1.17#semicolons and https://github.com/golang/go/issues/25192 for context.

See also: cf685fb5 (fixup! Y client: Fix URI scheme to move credentials out of query)

parse_qsl no longer treats ';' as valid query separator for security
reason because most proxies did not do so and it was possible to poison
proxy cache due to difference in query separator handling (see bugs.python.org/issue42967).

To handle credentials we don't have any proxy here, and it is still
perfectly valid to use ';' as credentials separator.

-> Fix it with ';' -> '&' replace workaround, before feeding credentials
string to parse_qsl.

Amends: b9a42957.