Add option lib-virt network with single tag

[2stacks]

I need a way to create a lib-virt network that when used by a kvm guest would add the guests vnic as an access port in a specific vlan in openvswitch. Some lib-virt integrations such as MAAS do not support adding a vnic to a specific 'portgroup'.

Ex. network created with virsh net-define

<network>
  <name>maas</name>
  <uuid>3f1a2ff2-8d90-4883-906b-6a818d8baabf</uuid>
  <forward mode='bridge'/>
  <bridge name='ovsbr0'/>
  <vlan>
    <tag id='193'/>
  </vlan>
  <virtualport type='openvswitch'/>
</network>

Adding a kvm guest to this network results in the following openvswitch output

ovs-vsctl show
a0a40804-5b4e-4133-b0a6-1b186d95e147
    Bridge "ovsbr0"
        Port "vnet0"
            tag: 193
            Interface "vnet0"
        Port "ovsbr0"
            Interface "ovsbr0"
                type: internal
        Port "enp4s0"
            Interface "enp4s0"
    ovs_version: "2.5.4"

[2stacks]

Here's the kvm guests network config after adding to this type of bridge.

    <interface type='bridge'>
      <mac address='52:54:00:0d:ea:75'/>
      <source network='maas' bridge='ovsbr0'/>
      <vlan>
        <tag id='193'/>
      </vlan>
      <virtualport type='openvswitch'>
        <parameters interfaceid='a9fcdcb8-8e98-4bb6-a6ac-65c81f7d4905'/>
      </virtualport>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </interface>