Actually connect to new validators at session boundary. (#3055)

* Actually connect to new validators at session boundary.

* Add tracing.

node/network/gossip-support/src/lib.rs

@@ -105,6 +105,11 @@ async fn determine_relevant_authorities(
  relay_parent: Hash,
 ) -> Result<Vec<AuthorityDiscoveryId>, util::Error> {
  let authorities = util::request_authorities(relay_parent, ctx.sender()).await.await??;
+ tracing::debug!(
+ target: LOG_TARGET,
+ authority_count = ?authorities.len(),
+ "Determined relevant authorities"
+ );
  Ok(authorities)
 }
 
@@ -137,7 +142,7 @@ impl State {
  for leaf in leaves {
  let current_index = util::request_session_index_for_child(leaf, ctx.sender()).await.await??;
  let maybe_new_session = match self.last_session_index {
- Some(i) if i <= current_index => None,
+ Some(i) if i >= current_index => None,
  _ => Some((current_index, leaf)),
  };