Revert D28338485: make ddp logging api to be private
Test Plan: revert-hammer
Differential Revision:
D28338485 (https://github.com/pytorch/pytorch/commit/ac44569b0d87ef7c2c8c26f3057f797f40cc6111)
Original commit changeset: bd2ae7c78904
fbshipit-source-id: d383f42a2051457147dec42ea273ed4fa82ffa1f
