all srs: use utils chart for rendering internal OS_AUTH_URL

[majewsky]

The current hardcoded pattern (http://keystone.$NAMESPACE.svc.$SEARCH_DOMAIN:5000/v3) will become incorrect when Keystone and Barbican move into a different namespace/cluster in certain regions because of regulatory requirements. By relying on the logic in openstack/utils, we will be dragged along when upstream changes the utils chart accordingly.

The new form looks slightly convoluted, but I'm following past precedent from other OpenStack charts for maximum compatibility.

Draft: openstack/utils is broken because it assumes that .Release.Namespace == "monsoon3". Therefore, this changeset results in tons of incorrect diffs like:

$ h diff upgrade -C 5 keppel helm-charts.git/openstack/keppel --namespace keppel --reset-values --normalize-manifests --find-renames 0.2 ...
keppel, keppel-api, Deployment (apps) has changed:
...
            valueFrom:
              secretKeyRef:
                key: trivy_token
                name: keppel-secret
          - name: OS_AUTH_URL
-           value: http://keystone.monsoon3.svc.<REDACTED>:5000/v3
+           value: http://keystone.keppel.svc.<REDACTED>:5000/v3
          - name: OS_AUTH_VERSION
            value: "3"
          - name: OS_IDENTITY_API_VERSION
            value: "3"
          - name: OS_INTERFACE
...