If distributed module isn't available, don't run distributed/pipeline tests (#53547)
Summary:
Following up https://github.com/pytorch/pytorch/issues/52945
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53547
Reviewed By: mrshenli
Differential Revision: D26946364
Pulled By: ezyang
fbshipit-source-id: 9f93e76e2420d19b46d4eb3429eac5f263fd5c23
