Refactor use of include_vars

Move all these 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.

The lookup order was taken from the openstack-ansible project, and
can be extended by copying the family vars file to a more specific
distro or versioned file and making necessary the changes, should
the need to complicate things ever arise again.

Change-Id: Ic3c0a072fc8d4cb10f6431c118f14afba3a3da1f

playbooks/roles/bifrost-ironic-install/defaults/dummy-defaults.yml

@@ -1,3 +0,0 @@
----
-# NOTE(cinerama) This file is intentionally left blank - do not
-# add variables here.

playbooks/roles/bifrost-ironic-install/tasks/main.yml

@@ -13,27 +13,18 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 ---
-# NOTE(cinerama) dummy-defaults.yml is an empty defaults file. We use it
-# here to ensure that with_first_found won't fail should we not have
-# defaults for a particular distribution, version, etc.
-- name: Include OS family-specific defaults
-  include_vars: "{{ item }}"
-  with_first_found:
-    - "../defaults/required_defaults_{{ ansible_os_family }}_family.yml"
-    - "../defaults/dummy-defaults.yml"
-
-- name: Include OS distribution-specific defaults
-  include_vars: "{{ item }}"
-  with_first_found:
-    - "../defaults/required_defaults_{{ ansible_distribution | regex_replace(' ', '_') }}.yml"
-    - "../defaults/dummy-defaults.yml"
-
-- name: Include OS version-specific defaults
-  include_vars: "{{ item }}"
-  with_first_found:
-    - "../defaults/required_defaults_{{ ansible_distribution | regex_replace(' ', '_') }}_{{ ansible_distribution_release }}.yml"
-    - "../defaults/required_defaults_{{ ansible_distribution | regex_replace(' ', '_') }}_{{ 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 Ironic deps"
   include_tasks: install.yml