private void evictCachedUserForGroup(JID user) {
        if (user != null) {

            // remove cache for getGroups
            synchronized (USER_GROUPS_LOCK) {
                clearUserGroupsCache(user);
            }
        }
    }
Returns the configured group provider. Note that this method has special access
privileges since only a few certain classes need to access the provider directly.

@return the group provider.
xmppserver/src/main/java/org/jivesoftware/openfire/group/GroupManager.java