[PG NCCL] Disable NCCL health check (#67668)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67668
This adds an env var to enable NCCL health check, which when left unspecified, results in the check not being run. Unit tests that need to test this functionality have the env variable set. Please see internal diff for more details.
Test Plan: CI
Reviewed By: yuguo68, mrshenli
Differential Revision: D32089763
fbshipit-source-id: dff5664a5e607f711515cd1042089ca769914fbb
