Merge pull request #1653 from edx/feanil/mongo_users

Create default mongo users.

playbooks/roles/mongo/defaults/main.yml

@@ -32,7 +32,7 @@ mongo_dbpath: "{{ mongo_data_dir }}/mongodb"
 
 # Have to use this conditional instead of ignore errors
 # because the mongo_user module fails and doesn't ignore errors.
-mongo_create_users: !!null
+mongo_create_users: true
 
 # If the system is running out of an Amazon Web Services
 # cloudformation stack, this group name can used to pull out