Adds C9 content provider with linting deps like C8

See depends-on and topic [1] for related reviews

[1] https://review.opendev.org/q/topic:c9_wallaby_gates
Depends-On: https://review.opendev.org/c/openstack/tripleo-ci/+/830132
Change-Id: I4ddfaf1c401e766e8b0613994b6c522b33b604b9

zuul.d/layout.yaml

@@ -13,10 +13,11 @@
       jobs:
         - openstack-tox-pep8
         - openstack-tox-tht
-        - tripleo-ci-centos-8-content-provider:
+        - tripleo-ci-centos-8-content-provider: &content_provider_deps
             dependencies:
               - openstack-tox-pep8
               - openstack-tox-tht
+        - tripleo-ci-centos-9-content-provider: *content_provider_deps
 
     gate:
       queue: tripleo