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/vault/tasks/shared/gen_userpass.yml

@@ -22,7 +22,7 @@
 - name: shared/gen_userpass | Copy credentials to all hosts in the group
   copy:
     content: >
-             {{ 
+             {{
              {'username': gen_userpass_username,
               'password': gen_userpass_password} | to_nice_json(indent=4)
              }}