make beg_size output deterministic for EmbeddingBag (#56661)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56661
Under some conditions (requires_grad = false and mode=SUM) bag_size and max_indices will be created via at::empty and will not be modified, that is why corresponding outputs is not deterministic and causing tests to fail.
Test Plan: buck test mode/opt //caffe2/benchmarks/static_runtime:static_runtime_cpptest -- --exact 'caffe2/benchmarks/static_runtime:static_runtime_cpptest - StaticRuntime.EmbeddingBag' --run-disabled
Reviewed By: hlu1
Differential Revision: D27931445
fbshipit-source-id: fe9747094027e4e6f7c7b0771c1cd994f94fd554
