Refactor distro vars include

We can simplify this logic a little.

Change-Id: Ib7429b7409e05af5b0b82e47c04633fe8e731cb8
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

tasks/main.yaml

@@ -13,12 +13,7 @@
 # under the License.
 ---
 - name: Include OS-specific variables
-  include_vars: "{{ ansible_distribution|lower }}.yaml"
-  when: ansible_os_family == 'Debian'
-
-- name: Include OS-specific variables
-  include_vars: "{{ ansible_os_family|lower }}.yaml"
-  when: ansible_os_family == 'RedHat'
+  include_vars: "{{ ansible_os_family | lower }}.yaml"
 
 - include: "{{ nodepool_task }}.yaml"
   with_items: "{{ nodepool_task_manager }}"