configurator: move usermod to spec

vdsm-tool configure --force adds to /etc/group (qemu/kvm) sanlock
but doesn't persist the file in ovirt node distro which will
affect vdsm start on next reboot. This patch adds the usermod to
spec file.

Change-Id: I8a44a8a4d3301263beeb03e1d106c25ffe85263e
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/26089
Reviewed-by: Dan Kenigsberg <danken@redhat.com>