'unplug vif:
1. delete the patch port pair between the integration bridge and
the qbr linux bridge(if exist) and the interim network.
2. destroy the interim network
3. delete the OVS bridge service for the interim network
4. delete linux bridge qbr and related ports if exist'

def unplug(self, instance, vif, vm_ref):

    super(XenAPIOpenVswitchDriver, self).unplug(instance, vif, vm_ref)
    net_name = self.get_vif_interim_net_name(vif['id'])
    network = network_utils.find_network_with_name_label(self._session, net_name)
    if (network is None):
        return
    vifs = self._session.network.get_VIFs(network)
    if vifs:
        return
    self.delete_network_and_bridge(instance, vif)
