virt-host-validate: Check those CGroups that we actually use

virt-host-validate: Check those CGroups that we actually use

Since the introduction of virt-host-validate tool the set of
cgroup controllers we use has changed so the tool is checking for
some cgroups that we don't need (e.g. net_cls, although I doubt
we have ever used that one) and is not checking for those we
actually use (e.g. cpuset).

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>