See parent issue for basic problem description. This subtask is for when total replication is used, with region based marshalling configured.

With region based marshalling, when a webapp undeploys, it inactivates its cache region. Thereafter, that region of the cache stops receiving updates from the rest of the cluster, and any data left in its persistent store can quickly get out of date with respect to the cluster. If the webapp, any persistent store data in the main tree is possibly out of date, superseded by data in another cache that has taken ownership of the session. So, the webapp's main tree region should be cleared before the region is activated. When the region is activated, the current correct state will be transferred.