message: Override the rpc_layer argument similar to the task_type and task_id.
diff: @@ -172,6 +172,7 @@ class TFConfigClusterResolver(ClusterResolver):
  # where available
  task_type = task_type if task_type is not None else self.task_type
  task_id = task_id if task_id is not None else self.task_id
  + rpc_layer = rpc_layer if rpc_layer is not None else self.rpc_layer
  return format_master_url(cluster_spec.task_address(task_type, task_id),
  - self.rpc_layer)
  + rpc_layer)
  