trap-manager: Properly check-in IKE_SA if initiating fails

This basically reverts f4e822c1b4 ("trap-manager: don't check-in
nonexisting IKE_SA if acquire fails").  As checkout_by_config() could
return an already existing and established IKE_SA we have to properly
destroy it, for instance, in case other threads are waiting to check
it out.  checkin_and_destroy() should handle the case of a new SA
properly (it produces a log message on level 1, though).

src/libcharon/sa/trap_manager.c

@@ -377,8 +377,8 @@ METHOD(trap_manager_t, acquire, void,
 		}
 		else
 		{
-			ike_sa->destroy(ike_sa);
-			charon->bus->set_sa(charon->bus, NULL);
+			charon->ike_sa_manager->checkin_and_destroy(charon->ike_sa_manager,
+														ike_sa);
 		}
 	}
 	peer->destroy(peer);