Support for removing repository markers for transient repositories

To support shared DSGC (disparate repositories), there's a new repository marker generated (also called clusterid)and stored in the node store and the meta space of the DataStore.
For transient repositories (designed to run one off jobs), it creates a problem as these repository markers stick around in the DataStore and prevent DSGC from sweeping.

There should be a configuration which should allow deletion of these repository markers on dispose. Transient repositories can then configure this and won't leave these zombies.