message: Seal queue when transitioning from joiner to validator
diff: @@ -233,6 +233,7 @@ impl Cli {
  // At this point, the joiner is shut down, so we clear the queue to ensure any
  // connections whose handshake completed but have not been registered are dropped.
  + joiner_queue.seal();
  for event in joiner_queue.drain_queues().await {
  debug!(event=%event, "drained event");
  }
  