libmodmount / do_umount_locked:
 * notify AVM components that a partition is being unmounted much earlier, this is NOT exactly the same what AVM does, but much closer to it as before (thanks to PeterPawn for pointing it out)
 * refs #2572


git-svn-id: file:///var/svn/freetz/trunk@12564 149334a1-2f27-0410-a3b9-fc62619ac1e6