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/bootstrap-os/tasks/main.yml

@@ -27,4 +27,3 @@
   hostname:
     name: "{{inventory_hostname}}"
   when: ansible_hostname == 'localhost'
-