Revert D30745961: [DDP] Remove self.modules_params
Test Plan: revert-hammer
Differential Revision:
D30745961 (https://github.com/pytorch/pytorch/commit/8c095102948c9601792a884dad56da5085c51bee)
Original commit changeset: 32d102502570
fbshipit-source-id: 59f7cc50d369b6cc2856cf4ebd0f58b96202336d
