[Wallaby only] Adding the multi-rhel job.

This add tripleo multi-rhel job to Wallaby testing.

Wallaby only as it's the only place where this multi-rhel state can
happen.

We add it to tripleo-upgrade where we will need that coverage in order
to ensure we adjust the command for successful multi-rhel update.

Depends-On: https://review.opendev.org/c/openstack/tripleo-ci/+/865851
Change-Id: I1384d3c6f290b109a10399c96680349af126dcd8

templates/overcloud_update_prepare.sh.j2

@@ -46,6 +46,10 @@ openstack overcloud update prepare ${PREPARE_ANSWER} \
     {% if config_heat_extra_yaml is defined -%}
     -e {{ working_dir }}/{{ install.deployment.files | basename }}/config_heat_extra.yaml \
     {% endif -%}
+    {% if mixed_os|default(false)|bool -%}
+    --disable-protected-resource-types \
+    --baremetal-deployment  \
+    {% endif -%}
     {% if rhsm_overcloud_env != '' -%}
     {# adding rhsm at the end so it overrides any other rhsm params passed. -#}
     -e /usr/share/openstack-tripleo-heat-templates/environments/rhsm.yaml \

zuul.d/layout.yaml

@@ -11,6 +11,7 @@
               - tripleo-upgrade-centos-8-molecule
         - openstack-tox-linters
         - tripleo-tox-molecule
+        - tripleo-ci-centos-8-content-provider: *content_provider_deps
         - tripleo-upgrade-centos-8-molecule:
             dependencies:
               - tripleo-tox-molecule
@@ -51,7 +52,12 @@
                 - build
             dependencies:
               - tripleo-ci-centos-9-content-provider
-
+        - tripleo-ci-centos-8-9-multinode-mixed-os-update:
+            irrelevant-files: *multinode_ignored
+            vars: *multi_consumer_vars
+            dependencies:
+              - tripleo-ci-centos-9-content-provider
+              - tripleo-ci-centos-8-content-provider
     gate:
       jobs:
         - openstack-tox-linters