Recurring Failures in QA E2E project.group.remove_via_api!

Summary

There appear to be a number of intermittent QA failures to remove groups via the api, with the following message

Failure/Error: group.remove_via_api!

QA::Resource::Errors::ResourceNotDeletedError:
  Resource at http://gitlab-ee-5cad5b5f.test/api/v4/groups/5?private_token=[****] could not be deleted (400): `{"message":"Group has been already marked for deletion"}`.

We should investigate why/what is causing the group to be already in a deleted state.