title: TensorFlow Distributed Estimator issue
body: <p>I was successful in getting a simple cluster with one of each: chief, parameter server, worker, evaluator to work. I followed the directions on the tf.estimator.train_and_evaluate page and set a stopping condition by setting train_spec.max_steps to 20000. My problem is that this is sufficient to stop the chief and worker, but the parameter server and evaluator continue to wait in a loop. Since I'm running under a batch scheduler and asked for a certain time limit, I have to wait until then to get my output. Is there any way to signal the parameter server and evaluator to exit when all the training is done?</p>