'unmarshalresult' object has no attribute 'server_name'
worker @ `stg` fails to start:

```
Unable to load celery application.
'unmarshalresult' object has no attribute 'server_name'
```
diff --git a/packit_service/config.py b/packit_service/config.py
index 3c1c6edd..dd01b5e8 100644
--- a/packit_service/config.py
+++ b/packit_service/config.py
@@ -112,7 +112,7 @@ class ServiceConfig(Config):
         # required to avoid circular imports
         from packit_service.schema import ServiceConfigSchema
 
-        config = ServiceConfigSchema().load(raw_dict)
+        config = ServiceConfigSchema().load_config(raw_dict)
 
         config.server_name = raw_dict.get("server_name", "localhost:5000")
 
['packit_service/config.py']