app_queue: Cleanup ao2_iterator

Clean ao2_iterator, resolving reference leak to queue members.

ASTERISK-24454 #close
Reported by: Corey Farrell
Review: https://reviewboard.asterisk.org/r/4111/
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Merged revisions 426255 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 426260 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@426266 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_queue.c

@@ -3496,6 +3496,7 @@ static void update_realtime_members(struct call_queue *q)
 			}
 			ao2_ref(m, -1);
 		}
+		ao2_iterator_destroy(&mem_iter);
 		ast_debug(3, "Queue %s has no realtime members defined. No need for update\n", q->name);
 		ao2_unlock(q);
 		return;