Comment 1 for bug 1970936

Reviewed: https://review.opendev.org/c/openstack/tripleo-heat-templates/+/839911
Committed: https://opendev.org/openstack/tripleo-heat-templates/commit/b72fa565994c599dce10f61df46e1939d705e06f
Submitter: "Zuul (22348)"
Branch: stable/train

commit b72fa565994c599dce10f61df46e1939d705e06f
Author: Harald Jensås <email address hidden>
Date: Sat Mar 28 03:47:06 2020 +0100

    Set dns_name propery on ports and networks

    Neutron's dns_assignments field includes a nice pice of
    structured data. This is a prerequirement for Designate
    usage. (No plan's to use that, but being a bit ready
    does'nt hurt.)

      {"hostname": "my-vm",
       "ip_address": "192.0.2.16",
       "fqdn": "my-vm.example.org."}

    Enable for the undercloud:
     - dns_domain_ports ml2 extension driver

    Need to backport this to train because network-v2 idempotency
    rely on the dns_doman. In Ie326f30fcc3d93533f4269cdfec40d3634684e22
    idempotency was change to use dns_domain instead of a neutron tag
    with the hostname because of neutron's limit on 60 chars per tag.

    Without this change the provisioning workflow will create duplicate
    ports when FFU upgrade is performed.

    Conflicts:
      overcloud.j2.yaml

    Closes-Bug: #1970936
    Change-Id: I46eb9a24dd66821b27524fe4d1fdab617b6fa948
    (cherry picked from commit 679ecaada05768e96a1fcddb7aeb78fc6735809f)