Add support for direct download in Swift storage engine

Fixes #483

util/config/validator.py

@@ -83,7 +83,7 @@ def _validate_registry_storage(config, _):
   driver = get_storage_provider(config)
 
   # Run custom validation on the driver.
-  driver.validate()
+  driver.validate(app.config['HTTPCLIENT'])
 
   # Put and remove a temporary file to make sure the normal storage paths work.
   driver.put_content('_verify', 'testing 123')