Because test attributes can constantly change in test lists, refstack-client
should have a native argument for passing in test lists (instead of '-- --load-list')
Refstack-client will normalize the tests in the given list by matching it to
test IDs in the current Tempest environment.
Closes-Bug: #1475407
Change-Id: I1e3f026f5cd706cf73b6febfce98cb96b742d4d6