Description of problem:
The guest was hang when stopped the cgconfig service
 
Version-Release number of selected component (if applicable):
libvirt-0.10.2-1.el6.x86_64
qemu-kvm-0.12.1.2-2.316.el6.x86_64
kernel-2.6.32-309.el6.x86_64

How reproducible:
100%
1 prepare the domain xml
# cat lxc.xml
<domain type='lxc'>
  <name>toy</name>
  <uuid>d1f4798b-bebf-d93c-1d97-fe1c1cb7c780</uuid>
  <memory>500000</memory>
  <currentMemory>500000</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type arch='x86_64'>exe</type>
    <init>/bin/sh</init>
  </os>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/libexec/libvirt_lxc</emulator>
    <interface type='network'>
      <mac address='52:54:00:25:bf:e9'/>
      <source network='default'/>
    </interface>
    <console type='pty'>
      <target type='lxc' port='0'/>
    </console>
  </devices>
</domain>

2 Define and start lxc guest.
# virsh -c lxc:/// define lxc.xml
# virsh -c lxc:/// start toy
# virsh -c lxc:/// list --all
 Id    Name                           State
----------------------------------------------------
 24294 toy                            running

3 Unmount cgroup 

  # /etc/init.d/cgconfig stop
  # /etc/init.d/cgconfig status
    Stopped
  # lscgroup

4 Then destoy the guest and found that the guest was hang
 # virsh -c lxc:/// destroy toy

5 Restart the libvirtd service and found that the guest was in "shut off" state 
  # /etc/init.d/libvirtd restart
  # virsh -c lxc:/// list --all
  Id    Name                           State
 ----------------------------------------------------
 -     toy                            shut off


Actual results:
The guest was hang when stopped the cgconfig service ,besides the guest was shutoff when restart the libvirtd service

Expected results:
the guest shouldn't be hang when stopped the cgconfig service and the guest should be still in "running"states when restart the libvirtd service 

Additional info