Don't stop slingId cleanup upon PROPERTIES_CHANGED

As a follow-up to SLING-10854 where the SlingIdCleanupTask was introduced. The current implementation stops cleanup when it received a PROPERTIES_CHANGED event. This is actually wrong. It should continue. The way it is currently done has the effect that cleanup is only triggered upon a TOPOLOGY_INIT or TOPOLOGY_CHANGED without a following PROPERTIES_CHANGED. This current behaviour reduces the chances of the cleanup running - having said that, the likelyhood of the cleanup eventually running is still very high.