@Test
  public void shutdownWithoutStart() throws IOException {
    AsyncRequestResponseHandler handler = getAsyncRequestResponseHandler(1);
    handler.shutdown();
  }
Tests for {@link AsyncRequestResponseHandler#shutdown()} when {@link AsyncRequestResponseHandler#start()} has not
been called previously. This test is for cases where {@link AsyncRequestResponseHandler#start()} has failed and
{@link AsyncRequestResponseHandler#shutdown()} needs to be run.
@throws IOException
ambry-rest/src/test/java/com/github/ambry/rest/AsyncRequestResponseHandlerTest.java