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/bootstrap/sync_vault_certs.yml

@@ -1,5 +1,4 @@
 ---
-
 - include: ../shared/sync_file.yml
   vars:
     sync_file: "ca.pem"
@@ -29,4 +28,3 @@
 - name: bootstrap/sync_vault_certs | Unset sync_file_results after api.pem sync
   set_fact:
     sync_file_results: []
-