message: Avoid setting `ConfigProto.cluster_def` when `run_config.cluster_def` is not set.
diff: @@ -140,7 +140,7 @@ def _obtain_topology(master_address, run_config):
  def _get_session_config_with_timeout(timeout_in_secs, run_config):
  cluster_def = None
  - if run_config.session_config and run_config.session_config.cluster_def:
  + if run_config.session_config and run_config.session_config.cluster_def.job:
  cluster_def = run_config.session_config.cluster_def
  config = config_pb2.ConfigProto(
  