@AfterClass
  public static void teardown() {
    if (plaintextNettyClient != null) {
      plaintextNettyClient.close();
    }
    if (sslNettyClient != null) {
      sslNettyClient.close();
    }
    if (ambryRestServer != null) {
      ambryRestServer.shutdown();
    }
  }
Shuts down the Ambry frontend server.
ambry-frontend/src/integration-test/java/com/github/ambry/frontend/FrontendIntegrationTest.java