[PyTorch Distributed] Move NCCL_DEBUG print to after NCCL init (#74287)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/74287
NCCL may read env vars from nccl.conf, it would be more accurate to get
envs after NCCL inits
Test Plan: unit test
Reviewed By: ajauhri
Differential Revision: D34912492
fbshipit-source-id: d794935573a59fd25f8cbfde6b64978e063e4d7a
(cherry picked from commit 2474cbd35d06938259952161800b6175b00ffc9a)
