endpoint snapshot: avoid second cleanup on alloc failure

In ast_endpoint_snapshot_create(), a failure to init the
string fields results in two attempts to ao2_cleanup the
same pointer.  Removed RAII_VAR to eliminate problem.

ASTERISK-25375 #close
Reported by: Scott Griepentrog

Change-Id: If4d9dfb1bbe3836b623642ec690b6d49b25e8979

main/endpoints.c

@@ -464,7 +464,7 @@ static void endpoint_snapshot_dtor(void *obj)
 struct ast_endpoint_snapshot *ast_endpoint_snapshot_create(
 	struct ast_endpoint *endpoint)
 {
-	RAII_VAR(struct ast_endpoint_snapshot *, snapshot, NULL, ao2_cleanup);
+	struct ast_endpoint_snapshot *snapshot;
 	int channel_count;
 	struct ao2_iterator i;
 	void *obj;
@@ -500,7 +500,6 @@ struct ast_endpoint_snapshot *ast_endpoint_snapshot_create(
 	}
 	ao2_iterator_destroy(&i);
 
-	ao2_ref(snapshot, +1);
 	return snapshot;
 }