Revert D31450501: Wextra caffe2/
Test Plan: revert-hammer
Differential Revision:
D31450501 (https://github.com/pytorch/pytorch/commit/7c2d3e6d327b500f15ae3c860f49bb7bc40d515e)
Original commit changeset: 702728fdb3c5
fbshipit-source-id: 486b8e872c38415706288f7f389d7cb1ea5eb0a9
