title: openstack instance task_state stuck in powering off, how reset it to None
body: <p>An instance execute <code>shutdown</code> in operation system, and the <code>power_state</code> is <code>Shutdown</code>, but the <code>vm_state</code> is <code>active</code> without shutdown the instance through API, and Why the <code>task_state</code> is always <code>powering-off</code>, event never execute other operation by API.</p>
  <p>Maybe the compute node memory is not enough at that time, and this instance was been killing, but now the compute node memory is satisfy.</p>
  <p>How can I set the <code>task_state</code> to <code>None</code> without change the database info?</p>
  <pre><code>openstack server show
  
  | OS-EXT-STS:power_state              | Shutdown         | 
  | OS-EXT-STS:task_state               | powering-off     | 
  | OS-EXT-STS:vm_state                 | active           | 
  
  
  openstack server reboot --hard
  
  Cannot 'reboot' instance instance-ID while it is in task_state powering-off (HTTP 409) (Request-ID: reqest-ID)
  </code></pre>
  <p><code>openstack server set --property OS-EXT-STS:task_state=None instance</code> not work, the <code>openstack server show</code> output not change.</p>