refine ldap create commands

- define gnuviechadmin.settins.base.CELERY_ROUTES to properly route ldap tasks
- return dummy values from osusers.tasks
- add billiard, kombu and pytz to requirements/base.txt

gnuviechadmin/osusers/tasks.py

@@ -5,9 +5,9 @@ from celery import shared_task
 
 @shared_task
 def create_ldap_group(group):
-    return group
+    return group.groupname
 
 
 @shared_task
 def create_ldap_user(user, password):
-    return user, password
+    return user.username