Add ability to restrict V1 push behind a namespace whitelist

Also enables the feature by default with an empty whitelist for QE

Fixes https://jira.coreos.com/browse/QUAY-1342

config_app/config_endpoints/api/suconfig.py

@@ -89,7 +89,6 @@ class SuperUserRegistryStatus(ApiResource):
   @nickname('scRegistryStatus')
   def get(self):
     """ Returns the status of the registry. """
-
     # If there is no config file, we need to setup the database.
     if not config_provider.config_exists():
       return {
@@ -104,7 +103,9 @@ class SuperUserRegistryStatus(ApiResource):
 
     config = config_provider.get_config()
     if config and config['SETUP_COMPLETE']:
-      return 'config'
+      return {
+        'status': 'config'
+      }
 
     return {
       'status': 'create-superuser' if not database_has_users() else 'config'