Fix https://github.com/pytorch/pytorch/issues/61982 (#66015)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66015
Fixes https://github.com/pytorch/pytorch/issues/61982 by clone of
tensors in DDPSink. Only applies once for static_graph and generally for unused
params which already has overhead, so perf hit should not be an issue. Will
verify with benchmark.
Test Plan: CI
Reviewed By: zhaojuanmao
Differential Revision: D31346633
fbshipit-source-id: 5b9245ade628565cffe01731f6a0dcbb6126029b
