Bug#51591 deadlock in the plugins+status+variables

Unlocking/locking of LOCK_plugin in ha_ndbcluster.cc not 
needed anymore (but missing from the initial patch).

sql/ha_ndbcluster.cc

@@ -7316,13 +7316,6 @@ static int ndbcluster_init(void *p)
   if (ndbcluster_inited)
     DBUG_RETURN(FALSE);
 
-  /*
-    Below we create new THD's. They'll need LOCK_plugin, but it's taken now by
-    plugin initialization code. Release it to avoid deadlocks.  It's safe, as
-    there're no threads that may concurrently access plugin control structures.
-  */
-  pthread_mutex_unlock(&LOCK_plugin);
-
   pthread_mutex_init(&ndbcluster_mutex,MY_MUTEX_INIT_FAST);
   pthread_mutex_init(&LOCK_ndb_util_thread, MY_MUTEX_INIT_FAST);
   pthread_cond_init(&COND_ndb_util_thread, NULL);
@@ -7463,8 +7456,6 @@ static int ndbcluster_init(void *p)
     goto ndbcluster_init_error;
   }
 
-  pthread_mutex_lock(&LOCK_plugin);
-
   ndbcluster_inited= 1;
   DBUG_RETURN(FALSE);
 
@@ -7477,8 +7468,6 @@ ndbcluster_init_error:
   g_ndb_cluster_connection= NULL;
   ndbcluster_hton->state= SHOW_OPTION_DISABLED;               // If we couldn't use handler
 
-  pthread_mutex_lock(&LOCK_plugin);
-
   DBUG_RETURN(TRUE);
 }