make tests for empty inputs check zero parameter grads (#32820)
Summary:
Make batch norm with empty inputs return zero parameter gradients. Now batch norm, group norm and convolutions now return zero grads for parameters, so make tests check that. Fixes some bullet points in https://github.com/pytorch/pytorch/issues/12013 (interpolate is not fixed by this PR, is being fixed in other PRs)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32820
Differential Revision: D19651470
Pulled By: ngimel
fbshipit-source-id: 96fdd085f9b0e98e91217dd2ac1f30f9c482b8be
