Fix fuse_func method overwrite (#87791) (#88193)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87791
Fixing the interface so that the fuse_func is honored and not replaced but the default fuse_known_method.
Test Plan: Wait for sandcastle
Reviewed By: jerryzh168
Differential Revision: D40722395
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88193
Approved by: https://github.com/jerryzh168
