CentOS 7 IPv6 doc changes

It advertises C7 as an IPv6-compatible platform.
This is possible thanks to fixes in [1] and [2].

[1] https://review.opendev.org/699458
aka 7054b27dbb
[2] https://review.opendev.org/699172
aka 908bffcfc2

Change-Id: Ia353a1663a16f48ac83e5ee9a2cf1d6e183ac3a3
Closes-bug: #1848444
Closes-bug: #1848452
Related-bug: #1856532
Related-bug: #1856725

doc/source/admin/production-architecture-guide.rst

@@ -104,7 +104,7 @@ the control plane using IPv6 instead of IPv4. Each Kolla Ansible network
 (as represented by interfaces) provides a choice of two address families.
 Both internal and external VIP addresses can be configured using an IPv6
 address as well.
-IPv6 is tested on Debian and Ubuntu.
+IPv6 is tested on all supported platforms.
 
 .. warning::
 
@@ -129,9 +129,6 @@ network. Current listing of networks is available in ``globals.yml`` file.
    While IPv6 support introduced in Train is broad, some services are known
    not to work yet with IPv6 or have some known quirks:
 
-   * CentOS 7 images suffer from IPv6 connectivity issues:
-     https://bugs.launchpad.net/kolla-ansible/+bug/1848444
-
    * Bifrost does not support IPv6:
      https://storyboard.openstack.org/#!/story/2006689
 
@@ -139,11 +136,6 @@ network. Current listing of networks is available in ``globals.yml`` file.
      https://github.com/moby/moby/issues/39033
      - the workaround is to use the hostname
 
-   * RabbitMQ in provided images prefers IPv4 addresses when resolving names:
-     https://bugs.launchpad.net/kolla-ansible/+bug/1848452
-     - the workaround is to ensure that the hostname resolves uniquely
-     to an IPv6 address
-
    * Ironic DHCP server, dnsmasq, is not currently automatically configured
      to offer DHCPv6: https://bugs.launchpad.net/kolla-ansible/+bug/1848454
 

releasenotes/notes/fix-centos-7-ipv6-39ac9207b8196ac7.yaml

@@ -0,0 +1,13 @@
+---
+fixes:
+  - |
+    Fixes IPv6 deployment on CentOS 7. The issues with RabbitMQ and
+    MariaDB have been worked around. For details please see the
+    following Launchpad bug records: `bug 1848444
+    <https://bugs.launchpad.net/kolla-ansible/+bug/1848444>`__,
+    `bug 1848452
+    <https://bugs.launchpad.net/kolla-ansible/+bug/1848452>`__,
+    `bug 1856532
+    <https://bugs.launchpad.net/kolla-ansible/+bug/1856532>`__ and
+    `bug 1856725
+    <https://bugs.launchpad.net/kolla-ansible/+bug/1856725>`__.