message: [network] Add some comments to connectivity manager
  Closes:
  Approved by: phlip9
diff: @@ -220,10 +220,10 @@ where
  .peer_addresses
  .iter()
  .filter(|(peer_id, addrs)| {
  - eligible.contains_key(peer_id)
  - && self.connected.get(peer_id).is_none()
  - && self.dial_queue.get(peer_id).is_none()
  - && !addrs.is_empty()
  + eligible.contains_key(peer_id) // The node is eligible to be dialed.
  + && self.connected.get(peer_id).is_none() // The node is not already connected.
  + && self.dial_queue.get(peer_id).is_none() // There is no pending dial to this node.
  + && !addrs.is_empty() // There is an address to dial.
  })
  .collect();
  