Gitaly: properly set PYTHON_TAG in CI, for Dockerfile (16.8)

What does this MR do?

Gitaly: properly set PYTHON_TAG in CI, for Dockerfile

See merge request !1710 (merged)

Merged-by: Hossein Pursultani hpursultani@gitlab.com Approved-by: Balasankar 'Balu' C balasankar@gitlab.com Approved-by: Hossein Pursultani hpursultani@gitlab.com Co-authored-by: Jason Plum jplum@gitlab.com

(cherry picked from commit abefaea0)

70df3637 Gitaly: properly set PYTHON_TAG in CI, for Dockerfile

Related issues

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated
• New dependencies are managed with dependencies.io