Add devstack ipv6 jobs

We can see that there is more demand on using ipv6 as the underlay
infrastructure to deploy new services, and OpenStack should be ready for
that.

These devstack ipv6 jobs are based on the work started by Jens Harbott in
https://review.openstack.org/#/c/608168/

Change-Id: I55bd067487665e5026e82a0737cb0f38a69499fb
Signed-off-by: aojeagarcia <aojeagarcia@suse.com>

.zuul.yaml

@@ -375,6 +375,19 @@
           VNCSERVER_LISTEN: 0.0.0.0
           VNCSERVER_PROXYCLIENT_ADDRESS: $HOST_IP
 
+- job:
+    name: devstack-ipv6
+    parent: devstack
+    description: |
+      Devstack single node job for integration gate with IPv6.
+    vars:
+      devstack_localrc:
+        SERVICE_IP_VERSION: 6
+        SERVICE_HOST: ""
+        # IPv6 and certificates known issue with python2
+        # https://bugs.launchpad.net/devstack/+bug/1794929
+        USE_PYTHON3: true
+
 - job:
     name: devstack-multinode
     parent: devstack
@@ -486,6 +499,8 @@
     check:
       jobs:
         - devstack
+        - devstack-ipv6:
+            voting: false
         - devstack-platform-centos-7
         - devstack-platform-opensuse-423
         - devstack-platform-opensuse-tumbleweed