Finish registering a new connection before sending routing update

[saketh-are]

Updates to the routing table trigger a broadcast advising all peers of the latest information:

nearcore/chain/network/src/peer_manager/network_state/routing.rs

Lines 36 to 41 in 9ddfd49

	fn broadcast_distance_vector(&self, distance_vector: DistanceVector) {
	let msg = Arc::new(PeerMessage::DistanceVector(distance_vector));
	for conn in self.tier2.load().ready.values() {
	conn.send_message(msg.clone());
	}
	}

Connection of a new peer is one type of event which results in a routing table update. The update should be broadcast after registering the new connection, so that the new peer is included in the broadcast.

[saketh-are]

This fix corrects an issue in which nodes don't converge correctly to the complete set of available routes. In the screenshot below, a node in a 3-node clique is aware of its direct connections to the other two nodes, but is not aware of the edge between its two peers.

After this change, the simple 3-node setup converges correctly.

[wacban]

LGTM