@Override
  public void run() {
    server.shutdown();
    try {
      server.awaitShutdown();
    } catch (InterruptedException e) {
      logger.warn("Server awaitShutdown is interrupted.");
    }
    latch.countDown();
  }
Shut down the servers and clean up the cluster.
@throws IOException
ambry-test-utils/src/main/java/com/github/ambry/server/MockCluster.java