Revert D30117838: [WIP] Gate DistributedOptimizers on RPC availability
Test Plan: revert-hammer
Differential Revision:
D30117838 (https://github.com/pytorch/pytorch/commit/3f09485d7e0c7466862cd6647b3668e119590716)
Original commit changeset: e6365a910a3d
fbshipit-source-id: f276b2b2bdf5f7bd27df473fca0eebaee9f7aef2
