child-rekey: Don't install outbound SA in case of lost collisions

This splits the SA installation also on the initiator, so we can avoid
installing the outbound SA if we lost a rekey collision, which might
have caused traffic loss depending on the timing of the DELETEs that are
sent in both directions.

src/libcharon/sa/ikev2/tasks/child_delete.c

@@ -196,7 +196,6 @@ static void install_outbound(private_child_delete_t *this,
 		/* FIXME: delete the new child_sa? */
 		return;
 	}
-	child_sa->set_state(child_sa, CHILD_INSTALLED);
 
 	my_ts = linked_list_create_from_enumerator(
 							child_sa->create_ts_enumerator(child_sa, TRUE));