message: [test] fix net test
diff: #[cfg(test)]
  mod tests {
  + use config::get_available_port;
  use futures::{
  channel::mpsc::{UnboundedReceiver, UnboundedSender},
  stream::StreamExt,
  @@ -30,7 +31,7 @@ mod tests {
  );
  fn build_test_network_pair(handle: Handle) -> (NetworkComponent, NetworkComponent) {
  - let mut l = build_test_network_services(2, 50400, handle).into_iter();
  + let mut l = build_test_network_services(2, get_available_port(), handle).into_iter();
  let a = l.next().unwrap();
  let b = l.next().unwrap();
  (a, b)
  