message: fix overpadding in MixtureSameFamily
diff: @@ -320,13 +320,14 @@ class MixtureSameFamily(distribution.Distribution):
  return array_ops.shape(d.batch_shape_tensor())[0]
  dist_batch_ndims = _get_ndims(self)
  cat_batch_ndims = _get_ndims(self.mixture_distribution)
  - bnd = distribution_util.pick_vector(
  + pad_ndims = distribution_util.pick_vector(
  self.mixture_distribution.is_scalar_batch(),
  - [dist_batch_ndims], [cat_batch_ndims])[0]
  + [dist_batch_ndims],
  + [dist_batch_ndims - cat_batch_ndims])[0]
  s = array_ops.shape(x)
  x = array_ops.reshape(x, shape=array_ops.concat([
  s[:-1],
  - array_ops.ones([bnd], dtype=dtypes.int32),
  + array_ops.ones([pad_ndims], dtype=dtypes.int32),
  s[-1:],
  array_ops.ones([self._event_ndims], dtype=dtypes.int32),
  ], axis=0))
  