Resize to the same host leaves original Representor plugged to br-int

[Adrian Chiris]

Description
===========
When using a Hardware offloaded OVS, attempting to perform a resize operation to the same host will leave the original representor port plugged to the OVS bridge (br-int)

Steps to reproduce
==================
1. Create representor port
$ openstack port create --network private --vnic-type=direct --binding-profile '{"capabilities": ["switchdev"]}' direct_port1
2. Create VMs using the ports created above:
openstack server create --flavor m1.tiny--image fedora24 --nic port-id=direct_port1 --availability-zone=nova:compute-1 vm1
3. Resize vm1
$ openstack server resize --flavor m1.small vm1
$ openstack server resize --confirm vm1
4. vm1 was resized, a new PCI device was allocated and its representor (eth2) plugged to OVS bridge: br-int, however the original representor (eth3) port is still attached to OVS
$ sudo ovs-dpctl show
system@ovs-system:
        lookups: hit:16694 missed:9695 lost:0
        flows: 1
        masks: hit:81980 total:1 hit/pkt:3.11
        port 0: ovs-system (internal)
        port 1: br-int (internal)
        port 2: br-enp3s0f0 (internal)
        port 3: br-ex (internal)
        port 4: enp3s0f0
        port 5: tapd5f4403d-86 (internal)
        port 6: qr-947ea2b7-da (internal)
        port 7: qg-a4baec0e-89 (internal)
        port 8: qr-2ea0d9f7-25 (internal)
        port 9: eth3
        port 10: eth2

Expected result
===============
After Resize, VM's previously used representor port should be unplugged from OVS.

Actual result
=============
VM's previously used representor port is still plugged.

Environment
===========
CentOS-7.6
Libvirt+KVM
$ /usr/libexec/qemu-kvm --version
QEMU emulator version 2.12.0
$ virsh --version
4.5.0
Neutron+OVS HW Offload
Deployment from Master (Nova: caa37cf099933c5aed02dcdb256055e18479fe13, Neutron: 513dd7f46bc9a1a7671366f0ab94ae0fccde25a1 )

[Adrian Chiris (adrian.chiris)]

since we are resizing to the same host, during nova.compute.manager.ComputeManager.confirm_resize() virt driver does not perform the vif.unplug() operation[1].

[1] https://github.com/openstack/nova/blob/2529ddfbe7940e90548175d6e2032383c38cda8f/nova/virt/libvirt/driver.py#L1262