* Remove some unused/uncallable iSCSI code in unshare_unmount().
  + Not called, because code was in a while(getmntent()) block,
    which only checks /etc/mtab, where iSCSI is never in...
* Call iscsi_disable_share_all() directly in unshare_unmount().
  Somewhat ugly hack (?), but there don't seem to be any other,
  obvious way to do it...