To test JENKINS-54057, i.e. the fact our rollback system wrt. data snapshotting does work, we need something that would actually make Jenkins fail to start if data is left on next UL state for instance.
We need to find or create a plugin that has a incompatible format change from version N to N+1. This way, we can include this in the upgrade/rollback test, and check that Jenkins does fail to restart after rollback.