[BB-983] Cleanup stale load balancer configuration fragments
Created by: lgp171188
This PR adds code to clean up the stale, leaked HAProxy configuration fragments created by the integration tests , which were piling up and causing the Let's Encrypt renewals to hang and start hitting the rate limits. See Sven's comment on BB-140 for more details.
Testing instructions:
- Log in to the stage load balancer.
- Update the creation and modification time of some of the
integration-*
files to older than 3 days. - Run the CI checks.
- Verify that the files were cleaned up and removed from the HAProxy configuration.