Revert D25607503: Add base forward grad logic
Test Plan: revert-hammer
Differential Revision:
D25607503 (https://github.com/pytorch/pytorch/commit/fdf02eff3d18cd6dd9ccbf073d69786409e14e01)
Original commit changeset: f1396290de1d
fbshipit-source-id: 057206e28ff48ee288856adfe3ca577d4880789f
