cleanup-test-artifacts: Preserve the test root dir
Do not delete /srv/images/test/ even if it becomes empty.
Deleting /srv/images/test/ caused error 403 to be returned, which confused the check in apertis-image-recipes@d619fc62.
Do not delete /srv/images/test/ even if it becomes empty.
Deleting /srv/images/test/ caused error 403 to be returned, which confused the check in apertis-image-recipes@d619fc62.