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/issue_cert.yml

@@ -26,7 +26,7 @@
 
 - name: issue_cert | Ensure target directory exists
   file:
-    path: "{{ issue_cert_path | dirname }}" 
+    path: "{{ issue_cert_path | dirname }}"
     state: directory
     group: "{{ issue_cert_file_group | d('root' )}}"
     mode: "{{ issue_cert_dir_mode | d('0755') }}"