message: Set the correct context when calling cudnnCreate.
  When running with multiple devices, using the wrong context will lead to
  a check-fail when trying to set a stream that has been created with a different
  context.
  This resolves a check-fail on resnet50 with 8 GPUs.
diff: @@ -322,6 +322,7 @@ port::Status GetLoadedCudnnVersion(CudnnVersion* version) {
  CudnnSupport::CudnnSupport(CUDAExecutor* parent) : parent_(parent) {}
  port::Status CudnnSupport::Init() {
  + ScopedActivateExecutorContext context(parent_);
  cudnnHandle_t cudnn_handle = nullptr;
  auto status = cudnnCreate(&cudnn_handle);
  if (status == CUDNN_STATUS_SUCCESS) {
  