title: gRPC issue on Ubuntu 17.10
body: <p>While running a TensorFlow test related to gRPC(<code>//tensorflow/core/debug:grpc_session_debug_test</code>)
  I get following error:</p>
  
  <pre><code>    self.server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
  AttributeError: 'module' object has no attribute 'server'
  </code></pre>
  
  <p>This appears only on Ubuntu 17.10.
  Works fine on Ubuntu 16.04</p>
  
  <p>I have installed following:</p>
  
  <pre><code>pip install futures grpc flask-socketio 
  </code></pre>
  
  <p>Is there some issue with gRPC on 17.10?
  Has anyone faced this error?</p>