Revert D22856816: [quant][fix] Remove activation_post_process in qat modules
Test Plan: revert-hammer
Differential Revision:
D22856816 (https://github.com/pytorch/pytorch/commit/8cb42fce17675142742d5fea78a067de4491d2cc)
Original commit changeset: 988a43bce46a
fbshipit-source-id: eff5b9abdfc15b21c02c61eefbda38d349173436
