Allow to override zun policy files

We implement `zun_policy_overrides` variable in order to allow
management of zun policy files when needed.

Change-Id: If58446a2ca1aa645e098df86c3d76c8ac94bf1a1

defaults/main.yml

@@ -368,3 +368,4 @@ zun_compute_init_overrides: {}
 zun_kuryr_init_overrides: {}
 zun_docker_init_overrides: {}
 zun_docker_cleanup_init_overrides: {}
+zun_policy_overrides: {}

releasenotes/notes/zun_policy_overrides-bc4e5d658969f0c8.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Added variable ``zun_policy_overrides`` that aims to allow deploying
+    policy.yaml file with provided overrides for Zun service.

tasks/zun_post_install.yml

@@ -60,6 +60,25 @@
     - zun-config
     - zun-post-install
 
+- name: Implement policy.yaml if there are overrides configured
+  config_template:
+    content: "{{ zun_policy_overrides }}"
+    dest: "/etc/zun/policy.yaml"
+    config_type: yaml
+  when:
+    - zun_policy_overrides | length > 0
+  tags:
+    - zun-policy-override
+
+- name: Remove legacy policy.yaml file
+  file:
+    path: "/etc/zun/policy.yaml"
+    state: absent
+  when:
+    - zun_policy_overrides | length == 0
+  tags:
+    - zun-policy-override
+
 - name: Synchronize the zun DB schema
   command: "{{ zun_bin }}/zun-db-manage --config-dir /etc/zun upgrade"
   become: yes