Fix container image builds

Container image builds broken due to disabling docker iptables
management in
https://review.opendev.org/c/openstack/kolla-ansible/+/751795. This
affects Wallaby and later.

This patch configures kolla-build to use network_mode=host.

Change-Id: I608c0362e6eeea65ffafb32cda5c19ccb6ec8b5c
Story: 2008942
Task: 42560

ansible/roles/kolla-build/templates/kolla-build.conf.j2

@@ -11,6 +11,10 @@ install_type={{ kolla_install_type }}
 # Docker namespace to use for Kolla images.
 namespace={{ kolla_docker_namespace }}
 
+# Use host networking by default, in line with Kolla Ansible's default Docker
+# engine configuration.
+network_mode=host
+
 # Docker image tag to apply.
 tag={{ kolla_tag }}
 

releasenotes/notes/kolla-build-network-mode-ba92e36d52e70d99.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes an issue with container image builds by using ``host`` as the default
+    ``network_mode`` for ``kolla-build``. See `story 2008942
+    <https://storyboard.openstack.org/#!/story/2008942>`__ for details.