Query cache usage can cause hanging

Problem does not reproduce with debug build.

gdb session shows that other node has a hanging slave applier thread inside Query_cache::invalidate_table()

Here is the stack trace of the hanging slave applier:

(gdb) bt
#0 0x004c0402 in __kernel_vsyscall ()
#1 0x00c582c6 in pthread_cond_wait@@GLIBC_2.3.2 ()
   from /lib/i686/nosegneg/libpthread.so.0
#2 0x0832e454 in Query_cache::invalidate_table ()
#3 0x0832e9de in Query_cache::invalidate_locked_for_write ()
#4 0x082bd21e in Rows_log_event::do_apply_event ()
#5 0x082c52be in wsrep_bf_execute_cb_rbr ()

Possibly relates to mysql bug: http://bugs.mysql.com/bug.php?id=43758

In our test case, slave applier is also waiting on condition: COND_cache_status_changed, but
somehow misses the signal.

Got hang when query cache was enabled, managed to save the following backtraces:

#0 __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136
#1 0x00007f5619cf560f in _L_lock_1172 () from /lib/libpthread.so.0
#2 0x00007f5619cf555a in __pthread_mutex_lock (mutex=0x7f5604058470)
    at pthread_mutex_lock.c:101
#3 0x00000000007767b8 in wsrep_innobase_kill_one_trx ()
#4 0x00000000007ce4bd in ?? ()
#5 0x00000000007d0ec2 in ?? ()
#6 0x00000000007d1991 in lock_clust_rec_read_check_and_lock ()
#7 0x0000000000808923 in ?? ()
#8 0x000000000080b67e in row_search_for_mysql ()
#9 0x0000000000777ebc in ha_innobase::index_read(unsigned char*, unsigned char const*, unsigned int, ha_rkey_function) ()
#10 0x0000000000777cd5 in ha_innobase::rnd_pos(unsigned char*, unsigned char*) ()
#11 0x000000000069b637 in Rows_log_event::find_row(Relay_log_info const*) ()
#12 0x000000000069cd5f in Update_rows_log_event::do_exec_row(Relay_log_info const*) ()
#13 0x000000000069fc05 in Rows_log_event::do_apply_event(Relay_log_info const*) ()
#14 0x00000000005e76b7 in ?? ()
#15 0x00007f56139a8674 in ?? () from /usr/lib/galera/libmmgalera.so
#16 0x00007f56139a9678 in process_query_write_set_applying ()
   from /usr/lib/galera/libmmgalera.so
#17 0x00007f56139a9fd4 in ?? () from /usr/lib/galera/libmmgalera.so
#18 0x00007f56139abeeb in ?? () from /usr/lib/galera/libmmgalera.so
#19 0x00000000005e624c in wsrep_replication_process(THD*) ()

#0 pthread_cond_wait@@GLIBC_2.3.2 ()
    at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162
#1 0x00000000007e7345 in os_event_wait_low ()
#2 0x000000000081ec05 in sync_array_wait_event ()
#3 0x0000000000820292 in mutex_spin_wait ()
#4 0x0000000000809cee in row_search_check_if_query_cache_permitted ()
#5 0x000000000077f49a in ?? ()
#6 0x000000000070f494 in Query_cache::ask_handler_allowance(THD*, TABLE_LIST*) ()
#7 0x0000000000712e27 in Query_cache::store_query(THD*, TABLE_LIST*) ()
#8 0x00000000005e40d8 in ?? ()
#9 0x00000000005e9cec in mysql_execute_command(THD*) ()
#10 0x00000000005ef3d1 in mysql_parse(THD*, char const*, unsigned int, char const**) ()
#11 0x00000000005f0e5f in dispatch_command(enum_server_command, THD*, char*, unsigned int)
    ()
#12 0x00000000005f1b71 in do_command(THD*) ()
#13 0x00000000005e06fd in handle_one_connection ()
#14 0x00007f5619cf29ca in start_thread (arg=<value optimized out>) at pthread_create.c:300
#15 0x00007f56191766cd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#16 0x0000000000000000 in ?? ()

Fix for 0.7.4 committed in http://bazaar.launchpad.net/~codership/codership-mysql/release-0.7/revision/3005