Revert D24941350: [pytorch][PR] Reopen PR for 0 dim batch size for AvgPool2d.
Test Plan: revert-hammer
Differential Revision:
D24941350 (https://github.com/pytorch/pytorch/commit/ceeab70da11a35c48604c0850aa880857594a360)
Original commit changeset: b7e50346d86e
fbshipit-source-id: 2e42e4418476658dc1afb905184841bf61688cfd
