Why not create a global prefs for show/visible logout button ?
if ($conf['user']['logout_button']) {
   Menu::printItem(Horde::url($registry->getParam('webroot', 'horde') .
'/login.php?reason=logout'),
        _("Logout"), 'logout.gif',  $registry->getParam('graphics',
"horde"));
}
>   Modified files:
>     templates            menu.inc
>   Log:
>   * Remove logout button