Don't run tests with custom arguments with pytest (#41397)
Summary:
This patch basically removes the `-m pytest` parameters when `extra_unittest_args` is used (e.g. `--subprocess`)
Fixes https://github.com/pytorch/pytorch/issues/41393
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41397
Reviewed By: pbelevich
Differential Revision: D22792133
Pulled By: ezyang
fbshipit-source-id: 29930d703666f4ecc0d727356bbab4a5f7ed4860
