chore: pin openstack deps (#391)

* chore: pin openstack deps

This commit adds infrastructure to pin OpenStack images which are
tagged by release in order to ensure the exact image is used in
a specific Atmosphere release.

It also adds an Earthfile which can automatically execute the
pinning.

* fix: allow for missing groups
diff --git a/.ansible-lint b/.ansible-lint
index b46745d..65e8cbd 100644
--- a/.ansible-lint
+++ b/.ansible-lint
@@ -5,6 +5,7 @@
   - charts
   - molecule
   - playbooks
+  - roles/defaults/defaults/main.ym
   - roles/kube_prometheus_stack/files/jsonnet
 
 warn_list: