RSU processor remains hanging

Fix pushed in: http://bazaar.launchpad.net/~codership/codership-mysql/wsrep-5.5/revision/3769

Regression test failed for wsrep-5.6 branch. Following assert was fired:

safe_mutex: Trying to unlock mutex that wasn't locked at /home/seppo/work/wsrep/wsrep-5.6-UKnoPA/wsrep-5.6/sql/mysqld.cc, line 5505
            Last used at /home/seppo/work/wsrep/wsrep-5.6-UKnoPA/wsrep-5.6/include/mysql/psi/mysql_thread.h, line: 1162
06:36:47 UTC - mysqld got signal 6 ;

...

stack_bottom = 7fa5f4046e48 thread_stack 0x40000
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(my_print_stacktrace+0x38)[0xadeec7]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(handle_fatal_signal+0x3f3)[0x74543d]
/lib/x86_64-linux-gnu/libpthread.so.0(+0xfbb0)[0x7fa5f91d4bb0]
/lib/x86_64-linux-gnu/libc.so.6(gsignal+0x37)[0x7fa5f8615f77]
/lib/x86_64-linux-gnu/libc.so.6(abort+0x148)[0x7fa5f86195e8]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(safe_mutex_unlock+0x8f)[0xae37e0]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld[0x615bf2]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld[0x6216ec]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(_Z39wsrep_wait_committing_connections_closei+0xbc)[0x6217fc]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld[0x635e69]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(_Z24wsrep_to_isolation_beginP3THDPcS1_PK10TABLE_LIST+0x3fe)[0x63682e]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(_Z21mysql_execute_commandP3THD+0x21e4)[0x7fb53f]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(_Z11mysql_parseP3THDPcjP12Parser_state+0x421)[0x8059ff]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld[0x804fee]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0x1067)[0x7f6e38]
2014-07-13 09:36:47 7832 [Note] WSREP: commit waiting for replaying: replayers 1, thd: (178) conflict: 0 (round: 1)
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(_Z10do_commandP3THD+0x6c7)[0x7f593a]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(_Z24do_handle_one_connectionP3THD+0x1be)[0x7bb863]
/home/seppo/work/testing/node1-shm-5.6/mysql/sbin/mysqld(handle_one_connection+0x33)[0x7bb366]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x7f6e)[0x7fa5f91ccf6e]
/lib/x86_64-linux-gnu/libc.so.6(clone+0x6d)[0x7fa5f86d99cd]

Fix pushed for wsrep-5.6 in revision:
http://bazaar.launchpad.net/~codership/codership-mysql/5.6/revision/4108

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXC-1232