gossipd: fix corner case where gossip msg too old after pending delay.

Happened under Travis with --dev-fast-gossip (90 second prune time), but can
happen anyway if gossip is almost 2 weeks old when we receive it:

2019-09-20T19:16:51.367Z DEBUG lightning_gossipd(20972): Received node_announcement for node 022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59
2019-09-20T19:16:51.376Z DEBUG lightning_gossipd(20972): Ignoring node_announcement timestamp 1569006918 for 022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59
2019-09-20T19:16:51.669Z **BROKEN** lightning_gossipd(20972): pending node_announcement 01013094af771d60f4de69bb39ce045e4edf4a06fe6c80078dfa4fab58ab5617d6ad4fa34b6d3437380db0a8293cea348bbc77f714ef71fcd8515bfc82336667441f00005d852546022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59022d2253494c454e544152544953542d633961313734610000000000000000000000000000 malformed? (version c9a174a)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

gossipd/routing.c

@@ -1454,13 +1454,12 @@ static void process_pending_node_announcement(struct routing_state *rstate,
 		    "Processing deferred node_announcement for node %s",
 		    type_to_string(pna, struct node_id, nodeid));
 
-		/* Should not error, since we processed it before */
+		/* Can fail it timestamp is now too old */
 		if (!routing_add_node_announcement(rstate,
 						   pna->node_announcement,
 						   pna->index))
-			status_failed(STATUS_FAIL_INTERNAL_ERROR,
-				      "pending node_announcement %s malformed?",
-				      tal_hex(tmpctx, pna->node_announcement));
+			status_unusual("pending node_announcement %s too old?",
+				       tal_hex(tmpctx, pna->node_announcement));
 		/* Never send this again. */
 		pna->node_announcement = tal_free(pna->node_announcement);
 	}
@@ -1836,13 +1835,15 @@ bool handle_pending_cannouncement(struct routing_state *rstate,
 	pending_cannouncement_map_del(&rstate->pending_cannouncements, pending);
 	tal_del_destructor2(pending, destroy_pending_cannouncement, rstate);
 
+	/* Can fail if channel_announcement too old */
 	if (!routing_add_channel_announcement(rstate, pending->announce, sat, 0))
-		status_failed(STATUS_FAIL_INTERNAL_ERROR,
-			      "Could not add channel_announcement");
-
-	/* Did we have an update waiting?  If so, apply now. */
-	process_pending_channel_update(rstate, scid, pending->updates[0]);
-	process_pending_channel_update(rstate, scid, pending->updates[1]);
+		status_unusual("Could not add channel_announcement %s: too old?",
+			       tal_hex(tmpctx, pending->announce));
+	else {
+		/* Did we have an update waiting?  If so, apply now. */
+		process_pending_channel_update(rstate, scid, pending->updates[0]);
+		process_pending_channel_update(rstate, scid, pending->updates[1]);
+	}
 
 	tal_free(pending);
 	return true;