Back out "[NCCL] DDP communication hook: getFuture()" (#42152)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42152
Original commit changeset: 8c059745261d
Test Plan: .
Reviewed By: ajtulloch, jianyuh
Differential Revision: D22786183
fbshipit-source-id: 51155389d37dc82ccb4d2fa20d350f9d14abeaca
