task: Do not remove Quay container on exit

[ibazulic]

When Quay container starts via the systemd unit, it gets automatically removed as a post-stop action. This causes problems when trying to diagnose startup issues, such as any validation errors. Logs are written in journal and can be pulled out by journalctl but sometimes it's just easier to call container logs instead. With this change, we set the removal of Quay container, if it exists, as an ExecStartPre action. This allows the container to persist after exiting for additional debugging.