Fix engine check for case where grad is a subclass (#65568)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/65568
Test Plan: Imported from OSS
Reviewed By: soulitzer
Differential Revision: D31158089
Pulled By: albanD
fbshipit-source-id: 2a77df9b6340107de02a043b57a36cb7ae68df34
