message: [network] fix conn_limit underflow error
  Connection limit was underflowing on an unsigned number causing panics.
  This should replace it without causing underflow.
  Closes:
  Approved by: phlip9
diff: @@ -348,7 +348,7 @@ where
  // including in flight dials.
  let to_connect_size = if let Some(conn_limit) = self.connection_limit {
  min(
  - conn_limit - self.connected.len() - self.dial_queue.len(),
  + conn_limit.saturating_sub(self.connected.len() + self.dial_queue.len()),
  to_connect.len(),
  )
  } else {
  