Fix comment in LockReleaseAll() on when locallock->nLock can be zero

We reach this case also e.g. when a deadlock is detected, not only
when we run out of memory.

Reviewed-by: Maxim Orlov
Discussion: https://www.postgresql.org/message-id/7c2090cd-a72a-4e34-afaa-6dd2ef31440e@iki.fi

Author: hlinnaka

src/backend/storage/lmgr/lock.c

@@ -2258,9 +2258,8 @@ LockReleaseAll(LOCKMETHODID lockmethodid, bool allLocks)
 	while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
 	{
 		/*
-		 * If the LOCALLOCK entry is unused, we must've run out of shared
-		 * memory while trying to set up this lock.  Just forget the local
-		 * entry.
+		 * If the LOCALLOCK entry is unused, something must've gone wrong
+		 * while trying to acquire this lock.  Just forget the local entry.
 		 */
 		if (locallock->nLocks == 0)
 		{