test-backport: fix extension tests
- Fixes extension test failures due to inadeqate test setup/cleanup.
- Adds back accidentally removed test for security patches
How to register an account on GitLab. To prevent spam, new accounts are locked until approved by an admin or the approver bot. You can also file an unlock request to expedite access.
Support: mw:GitLab, how to host a project on GitLab, #wikimedia-gitlab on libera.chat, #GitLab on Phabricator.