Fixup the test-certbot playbook to use set-vars

The test-certbot playbook was broken - referencing an unknown role.
And it did not use the `set-vars` role to properly initialize.

Now it uses `set-vars` and includes the local certbot role.

Adds to the fix for Issue #207

Author: freephile

src/playbooks/test-certbot.yml

@@ -2,4 +2,5 @@
   hosts: localhost
   become: true
   roles:
-    - certbot
+    - set-vars
+    - ansible-role-certbot-meza