Back out "[DDP] Disable reducer hooks from running outside of DDP backwards." (#61399)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61399
Reverts https://github.com/pytorch/pytorch/pull/60921
Original commit changeset: fef76a0dd295
ghstack-source-id: 133581300
Test Plan: CI
Differential Revision: D29594262
fbshipit-source-id: a308d3f10dbbb2169d9a7f60f2f28f139185ed1f
