linkbox_remove-function:
 * revise it, make it work the latest labors for 7390 & 7490
 * fixes the problem reported in [http://www.ip-phone-forum.de/showthread.php?t=271048 this thread]


git-svn-id: file:///var/svn/freetz/trunk@12172 149334a1-2f27-0410-a3b9-fc62619ac1e6