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/auth_backend.yml

@@ -1,11 +1,10 @@
 ---
-
 - name: shared/auth_backend | Test if the auth backend exists
   uri:
     url: "{{ vault_leader_url }}/v1/sys/auth/{{ auth_backend_path }}/tune"
     headers: "{{ vault_headers }}"
     validate_certs: false
-  ignore_errors: true 
+  ignore_errors: true
   register: vault_auth_backend_check
 
 - name: shared/auth_backend | Add the cert auth backend if needed