Refactor the use of include_vars

Move remaining os-default files to vars directory, where the
include_vars expects them to be.

Use a first_found lookup instead of a with_first_found loop so that
the 'paths' parameter can be used.

This ensures that only vars from the role are included, and not vars
from a parent calling role. This can happen when a parent role has
a higher priority vars file available for inclusion than the role
it calls.

Change-Id: I49c041b2217c51048fa182106009d334b6b38f6f

playbooks/roles/bifrost-create-vm-nodes/defaults/dummy-defaults.yml

@@ -1,2 +0,0 @@
----
-# Note(TheJulia): This file is intentionally left empty. Do not edit.

playbooks/roles/bifrost-create-vm-nodes/tasks/main.yml

@@ -23,18 +23,18 @@
     - ansible_distribution == "CentOS"
     - ansible_distribution_version|int >= 9
 
-- name: "Load distribution defaults"
-  include_vars: "{{ item }}"
-  with_first_found:
-    - "../defaults/required_defaults_{{ ansible_distribution }}.yml"
-    - "../defaults/required_defaults_{{ ansible_os_family }}.yml"
-
-- name: "Include OS version-specific defaults"
-  include_vars: "{{ item }}"
-  with_first_found:
-    - "../defaults/required_defaults_{{ ansible_distribution }}_{{ ansible_distribution_release }}.yml"
-    - "../defaults/required_defaults_{{ ansible_distribution }}_{{ ansible_distribution_version }}.yml"
-    - "../defaults/dummy-defaults.yml"
+- name: Gather variables for each operating system
+  include_vars: "{{ lookup('first_found', params) }}"
+  vars:
+    params:
+      files:
+        - "{{ ansible_facts['distribution'] | lower }}-{{ ansible_facts['distribution_version'] | lower }}.yml"
+        - "{{ ansible_facts['distribution'] | lower }}-{{ ansible_facts['distribution_major_version'] | lower }}.yml"
+        - "{{ ansible_facts['os_family'] | lower }}-{{ ansible_facts['distribution_major_version'] | lower }}.yml"
+        - "{{ ansible_facts['distribution'] | lower }}.yml"
+        - "{{ ansible_facts['os_family'] | lower }}.yml"
+      paths:
+        - "{{ role_path }}/vars"
 
 - name: "Install required packages"
   package: