Fix Bug#39438 Testcase for Bug#39436 crashes on 5.1 in fil_space_get_latch

In ha_innobase::info() - do not try to get the free space for a tablespace
which has been discarded with ALTER TABLE ... DISCARD TABLESPACE or if the
.ibd file is missing for some other reason.

ibd_file_missing and tablespace_discarded are manipulated only in
row_discard_tablespace_for_mysql() and in row_import_tablespace_for_mysql()
and the manipulation is protected/surrounded by
row_mysql_lock_data_dictionary()/row_mysql_unlock_data_dictionary() thus we
do the same in ha_innobase::info() when checking the values of those members
to avoid race conditions. I have tested the code-path with UNIV_DEBUG and
UNIV_SYNC_DEBUG.

Looks like it is not possible to avoid mysqld printing warnings in the
mysql-test case and thus this test innodb_bug39438 must be added to the
list of exceptional test cases that are allowed to print warnings. For this,
the following patch must be applied to the mysql source tree:

  --- cut ---
  === modified file 'mysql-test/lib/mtr_report.pl'
  --- mysql-test/lib/mtr_report.pl	2008-08-12 10:26:23 +0000
  +++ mysql-test/lib/mtr_report.pl	2008-10-01 11:57:41 +0000
  @@ -412,7 +412,10 @@
   
                   # When trying to set lower_case_table_names = 2
                   # on a case sensitive file system. Bug#37402.
  -                /lower_case_table_names was set to 2, even though your the file system '.*' is case sensitive.  Now setting lower_case_table_names to 0 to avoid future problems./
  +                /lower_case_table_names was set to 2, even though your the file system '.*' is case sensitive.  Now setting lower_case_table_names to 0 to avoid future problems./ or
  +
  +                # this test is expected to print warnings
  +                ($testname eq 'main.innodb_bug39438')
   		)
               {
                 next;                       # Skip these lines
  
  --- cut ---

The mysql-test is currently somewhat disabled (see inside
innodb_bug39438.test), after the above patch has been applied to the mysql
source tree, the test can be enabled.

rb://20

Reviewed by:	Inaam, Calvin
Approved by:	Heikki