Astobj2: Run weakproxy subscription callbacks in reverse order.

Modify ao2_weakproxy_subscribe so each new subscription is added
to the head of the list.  This ensures that when other objects
are allocated and use a subscription to the weakproxy for cleanup,
cleanup will occur in the correct order.

ASTERISK-25120 #close

Change-Id: Ie0476f08ec21330de1b3f5a2dd3d9eb683df3d3d

include/asterisk/astobj2.h

@@ -612,6 +612,8 @@ void *__ao2_weakproxy_get_object(void *weakproxy, int flags,
  * \retval 0 Success
  * \retval -1 Failure
  *
+ * \note Callbacks are run in the reverse order of subscriptions.
+ *
  * \note This procedure will allow the same cb / data pair to be added to
  *       the same weakproxy multiple times.
  *

main/astobj2.c

@@ -928,7 +928,7 @@ int ao2_weakproxy_subscribe(void *weakproxy, ao2_weakproxy_notification_cb cb, v
 		if (sub) {
 			sub->cb = cb;
 			sub->data = data;
-			AST_LIST_INSERT_TAIL(&weak->destroyed_cb, sub, list);
+			AST_LIST_INSERT_HEAD(&weak->destroyed_cb, sub, list);
 			ret = 0;
 		}
 	} else {