feat(redis): add ansible role

roles/redis/defaults/main/container.yml

@@ -17,8 +17,7 @@ redis_container_image: >-2
     + ':' +
     (redis_container_image_tag | default(
       redis_version + (
-        ((redis_container_image_flavour is string)
+        (redis_container_image_flavour | default(false, true) | bool)
-            and (redis_container_image_flavour | length > 0))
         | ternary('-' + (redis_container_image_flavour | default('')), '')
       ),
       true,