Solution for 5.0.
Changed calls to open_table(). Requested to ignore
flush at places where the command did already lock tables.
This could happen in CREATE ... SELECT and ALTER TABLE.

No test case. The bug can only be triggered by true concurrency.
The stress test suite provides a test case for this.


sql/sql_base.cc:
  Bug#12845 - Stress test: Server crashes on  CREATE .. SELECT statement
  Solution for 5.0.
  Changed open_table() so that ignoring flush requests
  is dependend on the 'flags' parameter as ignoring drop
  request was already. This aims for consistent behaviour.
sql/sql_table.cc:
  Bug#12845 - Stress test: Server crashes on  CREATE .. SELECT statement
  Solution for 5.0.
  Changed calls to open_table(). Requested to ignore
  flush at places where the command did already lock tables.
  This could happen in CREATE ... SELECT and ALTER TABLE.