Add protection for reinitialization of mutex in parallel replaction

Added mutex_lock/mutex_unlock of mutex that is to be destroyed in
wait_for_commit::reinit() in a similar fashion that we do in
~wait_for_commit

Author: montywi

sql/sql_class.cc

@@ -6516,7 +6516,13 @@ wait_for_commit::reinit()
 
     So in this case, do a re-init of the mutex. In release builds, we want to
     avoid the overhead of a re-init though.
+
+    To ensure that no one is locking the mutex, we take a lock of it first.
+    For full explanation, see wait_for_commit::~wait_for_commit()
   */
+  mysql_mutex_lock(&LOCK_wait_commit);
+  mysql_mutex_unlock(&LOCK_wait_commit);
+
   mysql_mutex_destroy(&LOCK_wait_commit);
   mysql_mutex_init(key_LOCK_wait_commit, &LOCK_wait_commit, MY_MUTEX_INIT_FAST);
 #endif