Print exitcode on failures in test_distributed.py (#35233)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/35233
Test Plan: Imported from OSS
Differential Revision: D20605264
Pulled By: mrshenli
fbshipit-source-id: f3d814943c88c2e2fa5da7e642bbcf9a405d08e6
