@Override
            public void entryUpdated(@Nonnull String key, @Nullable MUCRoom oldValue, @Nullable MUCRoom newValue, @Nonnull NodeID nodeID)
            {
            }
When the local node is joining or leaving a cluster, {@link org.jivesoftware.util.cache.CacheFactory} will swap
the implementation used to instantiate caches. This causes the cache content to be 'reset': it will no longer
contain the data that's provided by the local node. This method restores data that's provided by the local node
in the cache. It is expected to be invoked right after joining the cluster.

This method checks whether local occupant nicknames clash with remote ones. If a clash is detected, both
occupants are kicked out of the room.

({@link org.jivesoftware.openfire.cluster.ClusterEventListener#joinedCluster()} or leaving

@param occupantManager The occupant manager that contains local occupant registration.
@return The set of local occupants that is in the room after processing. This is the original set of local occupants of the room minus any occupants that were kicked out.
xmppserver/src/main/java/org/jivesoftware/openfire/muc/spi/LocalMUCRoomManager.java