Add tests for superuser config API calls

util/config/provider/testprovider.py

@@ -7,8 +7,11 @@ class TestConfigProvider(BaseProvider):
   """ Implementation of the config provider for testing. Everything is kept in-memory instead on
       the real file system. """
   def __init__(self):
+    self.clear()
+
+  def clear(self):
     self.files = {}
-    self._config = None
+    self._config = {}
 
   @property
   def provider_id(self):