This will use a top-level group if it's available, or create one if it's
not, then create our qa_test_* groups as subgroups of the sandbox
group.
See https://gitlab.com/gitlab-org/gitlab-ce/issues/37996
This does not yet fully address @grzesiek's note:
Note that we might want to pass top-level group name using an environment variable, and create one if environment variable is not set to make it work with any instance.