discovery: pass context to ProcessRemoteAnnouncement

With this, we move a context.TODO() out of the gossiper and into the
brontide package - this will be removed in a future PR which focuses on
threading contexts through that code.

discovery/gossiper.go

@@ -857,10 +857,8 @@ func (d *AuthenticatedGossiper) stop() {
 // then added to a queue for batched trickled announcement to all connected
 // peers.  Remote channel announcements should contain the announcement proof
 // and be fully validated.
-func (d *AuthenticatedGossiper) ProcessRemoteAnnouncement(msg lnwire.Message,
-	peer lnpeer.Peer) chan error {
-
-	ctx := context.TODO()
+func (d *AuthenticatedGossiper) ProcessRemoteAnnouncement(ctx context.Context,
+	msg lnwire.Message, peer lnpeer.Peer) chan error {
 
 	log.Debugf("Processing remote msg %T from peer=%x", msg, peer.PubKey())
 
@@ -950,8 +948,12 @@ func (d *AuthenticatedGossiper) ProcessRemoteAnnouncement(msg lnwire.Message,
 
 	// If the peer that sent us this error is quitting, then we don't need
 	// to send back an error and can return immediately.
+	// TODO(elle): the peer should now just rely on canceling the passed
+	//  context.
 	case <-peer.QuitSignal():
 		return nil
+	case <-ctx.Done():
+		return nil
 	case <-d.quit:
 		nMsg.err <- ErrGossiperShuttingDown
 	}