config: make sure to reload file after saving it

To ensure the configparser object is uptodate.

mylib/config.py

@@ -758,6 +758,7 @@ class Config:  # pylint: disable=too-many-instance-attributes
             log.exception(
                 'Failed to write generated configuration file %s', filepath)
             return False
+        self.load_file(filepath)
         return True
 
     @property