build-qa-image job does not work in Security Repo

Objective

Ensure that build-qa-image job works in gitlab-org/security/gitlab repo to support secure MRs. See https://gitlab.com/gitlab-org/security/gitlab/-/jobs/382490488 for an example of the failure.

Currently the image is pushed to https://registry.gitlab.com/v2/gitlab-org/security/gitlab/gitlab/gitlab-ee-qa/manifests/master which is not linked to a repo.

Proposal

Use the same repo as gitlab-org/gitlab qa images when the build-qa-image job is run from gitlab-org/security/gitlab.

Additional context

https://gitlab.slack.com/archives/C3JJET4Q6/p1576615361048700