[Torch] Correct launcher tests (#59635)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59635
The diff corrects launcher tests. The follow up would be to determine why the tests succeeded during the ``use_env`` diff removal
Test Plan: buck test mode/dev-tsan //caffe2/test/distributed/launcher:run_test -- --exact 'caffe2/test/distributed/launcher:run_test - test_launch_user_script_python_caffe2_bc (run_test.ElasticLaunchTest)' --run-disabled
Reviewed By: cbalioglu
Differential Revision: D28963813
fbshipit-source-id: a9f9b80787fb5c2f40a69ce31c8c2f3138654cad
