[Dist CI][BE] test_c10d_nccl run in subprocess (#68503)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68503
Per title
ghstack-source-id: 143928768
Test Plan: CI
Reviewed By: H-Huang
Differential Revision: D32484990
fbshipit-source-id: 6682f46256af0da5153e5087a91a7044156dd17f
