Tempest Exits Prematurely With Return Code of Zero

Issue

• The tests test_shelve_unshelve_server and test_shelve_shelved_server cause Tempest to exit prematurely, but with a return code of 0. Most automated testing systems would assume all tests were passed based on a successful return code. The problem is compounded when running tests concurrently, as the amount of tests completed before exiting will vary. Concurrent testing is the default behavior.