Packaging: Fix vdsm.prerm of Ubuntu packaging scripts

On Ubuntu, qemu-sanlock.conf is not used, so there is no need to
restore it during the packaging removal.

Change-Id: Ic7ead24ae6321339565252794210652d2a2b0bc6
Signed-off-by: Zhou Zheng Sheng <zhshzhou@linux.vnet.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/20169
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>