message: Fix warning in rnn_cell.py
  This fix fixes the warning in rnn_cell.py caused by l2_normalize with dim:
  ```
  rnn_cell.py:2894: calling l2_normalize (from tensorflow.python.ops.nn_impl) with dim is deprecated and will be removed in a future version.
  ```
diff: @@ -2891,7 +2891,7 @@ class WeightNormLSTMCell(rnn_cell_impl.RNNCell):
  output_size = weight.get_shape().as_list()[1]
  g = vs.get_variable(name, [output_size], dtype=weight.dtype)
  - return nn_impl.l2_normalize(weight, dim=0) * g
  + return nn_impl.l2_normalize(weight, axis=0) * g
  def _linear(self,
  args,
  