vdsm.spec: specify sysV commands for EL6 only

To provide EL7 builds we must update the spec to not
include sysV commands since it uses systemd.

Change-Id: Ie52ae97d48d795d53529152b68380fbd13d7927d
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1051860
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/23235
Reviewed-by: Dan Kenigsberg <danken@redhat.com>