Simplify async execution for script remote calls. (#53207)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53207
Simplifying some of the async execution logic in request_callback_impl
as part of https://github.com/pytorch/pytorch/issues/39351.
ghstack-source-id: 123004020
Test Plan: waitforbuildbot
Reviewed By: mrshenli
Differential Revision: D26791325
fbshipit-source-id: 790ad413dad410dbcd07787583674cb5af1d1c92
