Update qa/Dockerfile to be built from the project root context
What does this MR do?
- This cherry-picks https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31379.
- This updates
qa/Dockerfile
to support being built from the project root context - This updates the
build-qa-image
job to build the QA image from the project root context
The supporting omnibus-gitlab
MR should be merged at the same time: omnibus-gitlab!3496 (merged)
Edited by Rémy Coutable