Adding yamllinter to ci steps (#1556)

* Adding yaml linter to ci check

* Minor linting fixes from yamllint

* Changing CI to install python pkgs from requirements.txt

- adding in a secondary requirements.txt for tests
- moving yamllint to tests requirements

roles/etcd/handlers/backup.yml

@@ -43,4 +43,3 @@
     ETCDCTL_API: 3
   retries: 3
   delay: "{{ retry_stagger | random + 3 }}"
-