message: Don't run done callback till all handles are scheduled, and the code breaks out
  of the loop.
diff: @@ -453,7 +453,7 @@ class PartitionedCallOp : public AsyncOpKernel {
  },
  rendez, std::move(done), std::placeholders::_1);
  auto* refcounted_done = new ReffedStatusCallback(std::move(callback));
  - for (int i = 1; i < handles->size(); ++i) {
  + for (int i = 0; i < handles->size(); ++i) {
  refcounted_done->Ref();
  }
  @@ -507,6 +507,7 @@ class PartitionedCallOp : public AsyncOpKernel {
  });
  }
  }
  + refcounted_done->Unref();
  }
  string UniquifyFunctionName(const FunctionLibraryDefinition* function_library,
  