[resubmit] [pytorch][PR] Fix for num_threads==1 in OpenMP "parallel for" (#39533)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/39533
Test Plan: CI
Reviewed By: ngimel
Differential Revision: D21889269
fbshipit-source-id: 5ba13a0a3ec11edd0b6a7c3fdb35396b847a3d9e
