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/tasks/check_certs.yml

@@ -66,4 +66,3 @@
               {%- set _ = certs.update({'sync': True}) -%}
       {% endif %}
       {{ certs.sync }}
-