message: Copy cluster_def from TPUClusterResolver to session config
diff: @@ -89,7 +89,12 @@ def initialize_tpu_system(cluster_resolver=None):
  serialized_topology = output.numpy()
  else:
  master = cluster_resolver.master()
  + cluster_spec = cluster_resolver.cluster_spec()
  +
  session_config = config_pb2.ConfigProto(allow_soft_placement=True)
  + if cluster_spec:
  + session_config.cluster_def.CopyFrom(cluster_spec.as_cluster_def())
  +
  with ops.Graph().as_default():
  with session_lib.Session(config=session_config, target=master) as sess:
  serialized_topology = sess.run(tpu.initialize_system())
  