Add systemd-containers functional tests

Add functional tests for the Ubuntu systemd-container elements
introduced with I45651de2aa1b19bdeee301094f0bdffdd0a3b45c

These test the Xenial and Bionic guest images build on Xenial and
Bionic hosts.  I'm not sure it's worth the gate resources to also do
this on CentOS/Trusty at this point, so they're left out.

Change-Id: Ie9da9e22f5421999ac96750624f7d53bb0aa6160

.zuul.d/jobs.yaml

@@ -12,9 +12,11 @@
         - dib-functests-xenial-python3
         - dib-functests-xenial-python3-image
         - dib-functests-xenial-python3-extras
+        - dib-functests-xenial-python3-containers
         - dib-functests-bionic-python3
         - dib-functests-bionic-python3-image
         - dib-functests-bionic-python3-extras
+        - dib-functests-bionic-python3-containers
         - tripleo-buildimage-overcloud-full-centos-7
         - openstack-tox-lower-constraints
 
@@ -90,6 +92,19 @@
         - gentoo/build-succeeds
         - debian-minimal/stable-vm
 
+- job:
+    name: dib-functests-containers
+    description: |
+      These are tests for elements focused on containers or other
+      small deployments
+    abstract: true
+    voting: false
+    parent: dib-functests-base
+    vars:
+      dib_functests:
+        - ubuntu-systemd-container/bionic-build-succeeds
+        - ubuntu-systemd-container/xenial-build-succeeds
+
 # Trusty / Python 2 tests
 - job:
     name: dib-functests-trusty-python2
@@ -143,6 +158,14 @@
     nodeset: ubuntu-bionic
     voting: false
 
+- job:
+    name: dib-functests-bionic-python3-containers
+    description: |
+      The containers tests on a Bionic build host with Python 3
+    parent: dib-functests-containers
+    nodeset: ubuntu-bionic
+    voting: false
+
 # Xenial / Python3 tests
 - job:
     name: dib-functests-xenial-python3
@@ -170,6 +193,14 @@
       dib_functests_extra:
         - opensuse-minimal/opensuse423-build-succeeds
 
+- job:
+    name: dib-functests-xenial-python3-containers
+    description: |
+      The containers tests on a Xenial build host with Python 3
+    parent: dib-functests-containers
+    nodeset: ubuntu-xenial
+    voting: false
+
 # Centos 7 / Python2 tests
 - job:
     name: dib-functests-centos7-python2