Revert D28664514: [pytorch][PR] various TensorIterator speed improvements
Test Plan: revert-hammer
Differential Revision:
D28664514 (https://github.com/pytorch/pytorch/commit/8a28bbeeb90454f4282e2186ccceb72f6a0e2a91)
Original commit changeset: 2e03cf90b37a
fbshipit-source-id: fcad039b7dc823fec8afa694ab74a7ac5011f8ab
