message: Change type of device FLR not found error to NotFound.
diff: @@ -499,7 +499,7 @@ Status GetOrCreateKernelAndDevice(
  FunctionLibraryRuntime* flr =
  device == nullptr ? nullptr : ctx.func_lib(device);
  if (device != nullptr && flr == nullptr) {
  - return errors::Unavailable(
  + return errors::NotFound(
  "Unable to find a FunctionLibraryRuntime corresponding to device ",
  device->name());
  }
  