ho: On ho failure clear the subscriber connection

Forget about the ho_lchan inside the gsm_subscriber_connection
in case of a handover failure, also clear the gsm_subscriber_connection
pointer before the lchan is passed to the lchan_free routine.
diff --git a/openbsc/src/handover_logic.c b/openbsc/src/handover_logic.c
index 511742e..bc9d68e 100644
--- a/openbsc/src/handover_logic.c
+++ b/openbsc/src/handover_logic.c
@@ -232,6 +232,8 @@
 		return -ENODEV;
 	}
 
+	new_lchan->conn->ho_lchan = NULL;
+	new_lchan->conn = NULL;
 	llist_del(&ho->list);
 	talloc_free(ho);