Small changes/cleanup (#46950)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46950
Make sure that we're fusing in a fuse tests, and refactor to more concise API to check if fusions have happened.
Test Plan: Imported from OSS
Reviewed By: ansley
Differential Revision: D24805250
Pulled By: eellison
fbshipit-source-id: f898008a64b74e761bb5fe85f91b3cdf2dbdf878
