Allow to override placement policy files

We implement `placement_policy_overrides` variable in order to allow
management of placement policy files when needed.

Change-Id: If219ac80ceed2bf455a7de83b848c9d0a66371a4

defaults/main.yml

@@ -118,3 +118,4 @@ placement_services:
 placement_api_uwsgi_ini_overrides: {}
 placement_api_init_overrides: {}
 placement_placement_conf_overrides: {}
+placement_policy_overrides: {}

releasenotes/notes/osa/placement_policy_overrides-42fec8e157795d27.yaml

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

tasks/placement_post_install.yml

@@ -30,3 +30,22 @@
   notify:
     - Restart placement services
     - Restart uwsgi services
+
+- name: Implement policy.yaml if there are overrides configured
+  config_template:
+    content: "{{ placement_policy_overrides }}"
+    dest: "/etc/placement/policy.yaml"
+    config_type: yaml
+  when:
+    - placement_policy_overrides | length > 0
+  tags:
+    - placement-policy-override
+
+- name: Remove legacy policy.yaml file
+  file:
+    path: "/etc/placement/policy.yaml"
+    state: absent
+  when:
+    - placement_policy_overrides | length == 0
+  tags:
+    - placement-policy-override