Pull out aws keys to top-level vars.

playbooks/roles/edxapp/defaults/main.yml

@@ -13,12 +13,14 @@
 LMS_BASE: ''
 PREVIEW_LMS_BASE: ''
 CMS_BASE: ''
+AWS_ACCESS_KEY_ID:  ''
+AWS_SECRET_ACCESS_KEY:  ''
 
 #Use YAML references (& and *) and hash merge <<: to factor out shared settings
 #see http://atechie.net/2009/07/merging-hashes-in-yaml-conf-files/
 edxapp_generic_auth_config:  &edxapp_generic_auth
-  'AWS_ACCESS_KEY_ID':  ''
-  'AWS_SECRET_ACCESS_KEY':  ''
+  'AWS_ACCESS_KEY_ID':  "{{AWS_ACCESS_KEY_ID}}"
+  'AWS_SECRET_ACCESS_KEY': "{{AWS_SECRET_ACCESS_KEY}}"
   'SECRET_KEY':  ''
   'XQUEUE_INTERFACE':
     'basic_auth': [ 'edx',  'edx']