Disable old fuser internally (#48322)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48322
Disable old fuser internally. I would like to find where we are inadvertently setting the old fuser, but in the meantime I would like to land a diff that I know will 100% cause it not to be run, and verify that it fixes the issue.
Test Plan: sandcastle
Reviewed By: ZolotukhinM
Differential Revision: D25126202
fbshipit-source-id: 5a4d0742f5f829e536f50e7ede1256c94dd05232
