message: Fix copy_sharding. It mistakenly replaced the tensor.
diff: @@ -223,7 +223,7 @@ def copy_sharding(from_tensor, to_tensor, use_sharding_op=False):
  return to_tensor
  if use_sharding_op:
  - to_tensor = tf2xla.sharding(from_tensor)
  + to_tensor = tf2xla.sharding(to_tensor)
  attr_value = attr_value_pb2.AttrValue(s=sharding)
  # pylint: disable=protected-access
  to_tensor.op._set_attr('_XlaSharding', attr_value)
  