Detach an attached snapshot volume success on cinder, but failed on the array

In Huawei driver (stable/liberty), there's a bug about detach a snapshot volume.
When detach snapshot volume on OpenStack, it's success.
But the lun on array doesn't detached. So report the bug and fix it.

For details:
1. create snapshot volume.
def create_volume_from_snapshot(self, volume, snapshot):
   ......
   return {'ID': lun_info['ID'], # there's no 'provider_location'
       'lun_info': lun_info}

2. terminate connection.
def terminate_connection(self, volume, connector, **kwargs):
  """Delete map between a volume and a host."""
  initiator_name = connector['initiator']
  volume_name = huawei_utils.encode_name(volume['id'])
  lun_id = volume.get('provider_location') # the snapshot volume lun_id is always None.
  host_name = connector['host']
  lungroup_id = None

    ......