"virsh cpu-stats" command fails after tripleo_nova_libvirt service is restarted

Issue

• It is impossible to obtain CPU stats for existing instances after tripleo_nova_libvirt service is restarted:

  [root@compute-0 ~]# podman exec -it nova_libvirt virsh cpu-stats instance-0000001e
  error: Failed to retrieve CPU statistics for domain 'instance-0000001e'
  error: Requested operation is not valid: cgroup CPUACCT controller is not mounted