The test with memory restrictions randomly works or fails in buildbot
depending on server configurations. On my machine the original test
worked.
As the test was there to just check if the server crashes when run with
small memory configurations, I disabled testing if the query would fail
or not. The test still has its original purpose.
Discussed with: Sergei Golubchik <serg@mariadb.org>
perfschema thread walker needs to take thread's LOCK_thd_kill to prevent
the thread from disappearing why it's being looked at.
But there's no need to lock it for the current thread.
In fact, it was harmful as some code down the stack might take
LOCK_thd_kill (e.g. set_killed() does it, and my_malloc_size_cb_func()
calls set_killed()). And it caused a bunch of mutexes being locked under
LOCK_thd_kill, which created problems later when my_malloc_size_cb_func()
called set_killed() at some unspecified point under some
random mutexes.
