Do not send regular status updates during syncing (#1375)

beacon_node/eth2_libp2p/src/peer_manager/mod.rs

@@ -714,6 +714,9 @@ impl<TSpec: EthSpec> Stream for PeerManager<TSpec> {
             }
         }
 
+        // We don't want to update peers during syncing, since this may result in a new chain being
+        // synced which leads to inefficient re-downloads of blocks.
+        if !self.network_globals.is_syncing() {
             loop {
                 match self.status_peers.poll_next_unpin(cx) {
                     Poll::Ready(Some(Ok(peer_id))) => {
@@ -726,6 +729,7 @@ impl<TSpec: EthSpec> Stream for PeerManager<TSpec> {
                     Poll::Ready(None) | Poll::Pending => break,
                 }
             }
+        }
 
         if !self.events.is_empty() {
             return Poll::Ready(Some(self.events.remove(0)));