MT#55283 remove reciprocal subscriptions

During offer/answer, we remove existing subscriptions before
re-establishing the new set of subscriptions. But we must also remove
the subscriptions of previous subscribers in order to keep the lists of
subscriptions and subscribers correctly reciprocal.

Change-Id: I7d39fa59892159f41033ae6a40e7cb51d861b12e

daemon/call.c

@@ -3015,7 +3015,9 @@ static void __unsubscribe_all_offer_answer_subscribers(struct call_monologue *ml
 			continue;
 		}
 		GList *next = l->next;
-		__unsubscribe_one(cs->monologue, ml);
+		struct call_monologue *other_ml = cs->monologue;
+		__unsubscribe_one(other_ml, ml);
+		__unsubscribe_one(ml, other_ml);
 		l = next;
 	}
 }