images: update command requires string id in server

ogserver expects a string as an id, otherwise it fails to parse it.

cli/objects/images.py

@@ -213,7 +213,7 @@ class OgImage():
                    'backup': parsed_args.backup,
                    'disk': parsed_args.disk,
                    'center_id': center_id,
-                   'id': parsed_args.id,
+                   'id': str(parsed_args.id),
                    'code': str(fs_code),
                    'name': image_name}