message: Fix race in test server test
diff: @@ -540,12 +540,12 @@ fn test_unused_server_cleanup() {
  let success = success.clone();
  std::thread::spawn(move || {
  let server = NatsTestServer::build().spawn();
  - std::thread::sleep(Duration::from_millis(1));
  + std::thread::sleep(Duration::from_millis(100));
  std::mem::drop(server);
  success.store(true, Ordering::Release);
  });
  }
  - std::thread::sleep(Duration::from_millis(2));
  + std::thread::sleep(Duration::from_millis(500));
  assert!(success.load(Ordering::Acquire));
  }
  