Back out "Dropout support for memory efficient attention (#102038)" & "Two small mem_eff bug fixes (#103201)" (#103464)
Summary:
Original commit changeset: 04c4473d8510
Original Phabricator Diff: D46584152 & D46582033
Test Plan: Already explained in summary.
Reviewed By: yinghai
Differential Revision: D46633283
fbshipit-source-id: c23c2945408988f3c4339dfd5cd40ae46261716c
Co-authored-by: Shenxiu Liu <shenxiu@meta.com>
