Add non-voting rolling upgrade test

This patch implements a replacement of the legacy rolling
upgrade test previously implemented. The job and pipeline
is defined in-repo to ensure that the keystone team has
complete control over the voting status, pipelines it is
in, etc.

The test uses the 'upgrade' tox environment in the
openstack/openstack-ansible-os_keystone repository which
executes a build of two keystone containers using the
the head of the stable branch of keystone, then upgrades
to the proposed review. The upgrade is a complete rolling
upgrade using MariaDB as a database.

Depends-On: If39e4bec8db0be04b13dfc005ee404b73c0b65d3
Depends-On: Ia5ab6aa43f912b3cb4adf98154cd3da12688c2e0
Change-Id: I78bb5e18c1ce0ddf18494f7cd0ef1ab6953be771

.zuul.yaml

@@ -0,0 +1,37 @@
+---
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This job will execute 'tox -e upgrade' from the OSA
+# repo specified in 'osa_test_repo'.
+- job:
+    name: openstack-ansible-keystone-rolling-upgrade
+    parent: openstack-ansible-cross-repo-functional
+    voting: false
+    required-projects:
+      - name: openstack/openstack-ansible-os_keystone
+    irrelevant-files:
+      - ^.*\.rst$
+      - ^api-ref/.*$
+      - ^doc/.*$
+      - ^etc/.*$
+      - ^keystone/tests/unit/.*$
+      - ^releasenotes/.*$
+    vars:
+      tox_env: upgrade
+      osa_test_repo: "openstack/openstack-ansible-os_keystone"
+
+- project:
+    name: openstack/keystone
+    check:
+      jobs:
+        - openstack-ansible-keystone-rolling-upgrade