Vif-plug event was been sent to old node cause evacuating failed

[zhangjialong]

Description
===========
When using host-evacuate command, some vms on failed host would be failed when evacuating because
the vif-plug event was be sent to failed node not the node which vm launched on.

Steps to reproduce
==================
1.create 8 vms on host1

2.nova service-force-down host1 nova-compute
  nova service-force-down host1 nova-conductor
  nova service-force-down host1 nova-scheduler

3.evacuate the vms on host1
  nova host-evacuate host1

Expected result
===============
After the execution of the steps above, all of vms on hosts1 should be evacuated to other hosts

Actual result
=============
only 2-3 vms can be evacuated, others became to failed

Environment
===========
1. My openstack version is mitaka

2. Use Libvirt + Kvm in OpenStack

2. Use Ceph as backend storage

3. Use Neutron with OpenVSwitch

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/mitaka
Review: https://review.openstack.org/355843

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/361059

[OpenStack Infra (hudson-openstack)]

Change abandoned by zhangjl (<email address hidden>) on branch: stable/mitaka
Review: https://review.openstack.org/355843
Reason: According to Lee Yarwood`s advice, it`s better to fix this bug on master, and then
cherry pick it back to mitaka.

And the master patch is here:

https://review.openstack.org/#/c/361059/

Thanks

[OpenStack Infra (hudson-openstack)]

Change abandoned by zhangjl (<email address hidden>) on branch: master
Review: https://review.openstack.org/361059