gitserver: use TLS configuration when pushing
Created by: LawnGnome
Fixes #31010 (closed).
Test plan
Manually tested against a self-signed GitLab instance; tested against bitbucket.sgdev.org to make sure nothing unexpected broke. Unit tests continue to pass because in theory there should be no behavioural change in the normal case; further automated testing has insufficient ROI (we'd need internal infrastructure just for this edge case).