lchan: Change transaction to work on the GSM Subscriber Connection

Change the MSC transaction code to operate on a GSM Subscriber Connection
instead of the lchan. This will help us to separate the two commands properly.
diff --git a/openbsc/src/handover_logic.c b/openbsc/src/handover_logic.c
index acb3aa1..7fb0b13 100644
--- a/openbsc/src/handover_logic.c
+++ b/openbsc/src/handover_logic.c
@@ -227,7 +227,7 @@
 	bsc_del_timer(&ho->T3103);
 
 	/* update lchan pointer of transaction */
-	trans_lchan_change(ho->old_lchan, new_lchan);
+	trans_lchan_change(&ho->old_lchan->conn, &new_lchan->conn);
 
 	ho->old_lchan->state = LCHAN_S_INACTIVE;
 	lchan_auto_release(ho->old_lchan);