Automated GitLab QA as part of staging deploy

Part of https://gitlab.com/gitlab-org/release/framework/issues/54

While we already have gitlab-qa running on staging on schedule, we should be adding this to our deployment pipelines.

GitLab QA can run specific scenarios on demand (no longer runs the whole suite). This means that we can add a new stage in the deployment pipeline that would have these separate jobs. We should start with having the few most important scenarios like project creation/cloning and docker push/pull.