Treat missing driver cgroup as fatal in LXC driver

The LXC driver relies on use of cgroups to kill off LXC processes
in shutdown. If cgroups aren't available, we're unable to kill
off processes, so we must treat lack of cgroups as a fatal startup
error.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
(cherry picked from commit 7c5ba648f7)

src/lxc/lxc_cgroup.c

@@ -229,10 +229,6 @@ int virLXCCgroupSetup(virDomainDefPtr def)
 
     rc = virCgroupForDriver("lxc", &driver, 1, 0);
     if (rc != 0) {
-        /* Skip all if no driver cgroup is configured */
-        if (rc == -ENXIO || rc == -ENOENT)
-            return 0;
-
         virReportSystemError(-rc, "%s",
                              _("Unable to get cgroup for driver"));
         goto cleanup;