Fix API_URL reinitialisation error

Author: luffah

src/nextcloud/__init__.py

@@ -61,7 +61,9 @@ def __init__(self, endpoint=None,
         for functionality_class in API_WRAPPER_CLASSES:
             # @FIX_API_URL {{
             if api_url_base:
-                functionality_class.API_URL = api_url_base + functionality_class.API_URL
+                if not getattr(functionality_class, '_ORIG_API_URL', False):
+                    functionality_class._ORIG_API_URL = functionality_class.API_URL
+                functionality_class.API_URL = api_url_base + functionality_class._ORIG_API_URL
             # }}
             functionality_instance = functionality_class(self)
             for potential_method in dir(functionality_instance):