message: Fix a use-after-scope
diff: @@ -1003,7 +1003,8 @@ struct FusedBatchNormGrad<GPUDevice, T, U> {
  std::unique_ptr<functor::CudnnBatchNormAllocatorInTemp<uint8>>
  workspace_allocator;
  - DeviceMemory<uint8>* reserve_space_data = nullptr;
  + DeviceMemory<uint8>* reserve_space_data_ptr = nullptr;
  + DeviceMemory<uint8> reserve_space_data;
  #if CUDNN_VERSION >= 7402
  if (use_reserved_space) {
  const Tensor& reserve_space = context->input(5);
  @@ -1013,9 +1014,9 @@ struct FusedBatchNormGrad<GPUDevice, T, U> {
  // the cudnn kernel outputs inverse variance in forward and reuse it in
  // backward
  if (reserve_space.dims() != 0) {
  - auto reserve_space_uint8 = functor::CastDeviceMemory<uint8, U>(
  + reserve_space_data = functor::CastDeviceMemory<uint8, U>(
  const_cast<Tensor*>(&reserve_space));
  - reserve_space_data = &reserve_space_uint8;
  + reserve_space_data_ptr = &reserve_space_data;
  }
  }
  #endif // CUDNN_VERSION >= 7402
  @@ -1026,7 +1027,7 @@ struct FusedBatchNormGrad<GPUDevice, T, U> {
  y_backprop_ptr, x_ptr, scale_ptr, mean_ptr, inv_variance_ptr,
  x_desc, scale_offset_desc, static_cast<double>(epsilon),
  &x_backprop_ptr, &scale_backprop_ptr, &offset_backprop_ptr,
  - reserve_space_data, workspace_allocator.get())
  + reserve_space_data_ptr, workspace_allocator.get())
  .ok();
  if (!cudnn_launch_status) {
  