Pass through TOP_UPSTREAM_SOURCE_REF for qa pipeline

What does this MR do?

Pass through CI_COMMIT_SHA_REF as TOP_UPSTREAM_SOURCE_REF variable to downstream omnibus-gitlab-mirror and gitlab-qa pipelines.

This variable is required for gitlab-qa to determine the upstream ref of triggered pipelines.

https://gitlab.com/gitlab-org/quality/team-tasks/issues/298

Conformity

• Code review guidelines
• Style guides