protected void checkObsolete( String verHash ) {
        if ( entityCapabilitiesUserMap.containsValue( verHash ) )
        {
            return;
        }

        entityCapabilitiesMap.remove( verHash );
    }
Verifies if the provided 'ver' hash is used for any user. If not, the cache entry
containing the entity capabilities are removed from the cache.

@param verHash an 'ver' hash (cannot be null).
xmppserver/src/main/java/org/jivesoftware/openfire/entitycaps/EntityCapabilitiesManager.java