channeld: send correct channel_update when reporting failure.

The master tells us the short_channel_id of the outgoing channel, and
channeld is supposed to get the corresponding channel_update from gossipd.
Instead, it got the channel_update for the *local* channel and ignored
that one.

channeld/channel.c

@@ -1745,7 +1745,7 @@ static void send_fail_or_fulfill(struct peer *peer, const struct htlc *h)
 		if (h->failcode) {
 			/* Local failure, make a message. */
 			u8 *failmsg = make_failmsg(tmpctx, peer, h, h->failcode,
-						   &peer->short_channel_ids[LOCAL]);
+						   h->failed_scid);
 			onion = create_onionreply(tmpctx, h->shared_secret,
 						  failmsg);
 		} else /* Remote failure, just forward. */