Pull in vars_files for all frontend apps that need databases.

The defaults need to be provided so that credentials get created properly.

playbooks/edx-persistance.yml

@@ -8,6 +8,12 @@
   hosts: all
   sudo: True
   gather_facts: True
+  vars_files:
+    - roles/edxapp/defaults/main.yml
+    - roles/forum/defaults/main.yml
+    - roles/xqueue/defaults/main.yml
+    - roles/ecommerce/defaults/main.yml
+    - roles/ecomworker/defaults/main.yml
   roles:
     # This install mysql and creates users.
     - role: edxlocal