libvirt_configure: persist /etc/libvirt/qemu-sanlock.conf

Fix missing persist of qemu-sanlock.conf file which affects
vdsm start when validating if the file were previously
configured.

Change-Id: I299f5cb7af4d2e09208835aeda28ec1f3c3def7d
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/27335
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>