Revert D25563542: Add batched grad testing to gradcheck, turn it on in test_autograd
Test Plan: revert-hammer
Differential Revision:
D25563542 (https://github.com/pytorch/pytorch/commit/443412e68249c32a59d10c76794a545e443a123b)
Original commit changeset: 125dea554abe
fbshipit-source-id: 0564735f977431350b75147ef209e56620dbab64
