Revert D31005792: [NCCL] Init dummy NCCL comms in constructor
Test Plan: revert-hammer
Differential Revision:
D31005792 (https://github.com/pytorch/pytorch/commit/2b22a5dde2a23f26bc7adec89940fba3f418349d)
Original commit changeset: c2c582dee25a
fbshipit-source-id: d8e962b8aab6fda8a6c013e8577492dff9568c27
