Add loop var policy to ansible-lint

This adds a custom ansible-lint rule at .rules/ZuulJobsNamespaceLoopVar.py
that enforces the loop var policy described at:
https://zuul-ci.org/docs/zuul-jobs/policy.html#ansible-loops-in-roles

It also updates existing roles to follow the policy.

Change-Id: I92b2ff56a1c2702542fc07b316f1809087a4c92f

playbooks/helm/run.yaml

@@ -3,6 +3,8 @@
     - include_role:
         name: helm-template
       vars:
-        helm_release_name: "{{ item.key }}"
-        helm_chart: "{{ item.value }}"
+        helm_release_name: "{{ zj_item.key }}"
+        helm_chart: "{{ zj_item.value }}"
       loop: "{{ helm_charts | dict2items }}"
+      loop_control:
+        loop_var: 'zj_item'