Revert D28494073: [Gradient Compression] Do not skip the comm hook tests for Gloo/MPI backends
Test Plan: revert-hammer
Differential Revision:
D28494073 (https://github.com/pytorch/pytorch/commit/df44f015fe1403f0fea54b46736c07550bb85870)
Original commit changeset: 6ba14082f986
fbshipit-source-id: 0e094f09b59c93f5ee13a667aacfb3ccf608547e
