MK8S-25: Fix create_index() to use _get_index_file_paths() directly

Complete the factorization by making create_index() consistent with clean():
- Both functions now iterate over the same _get_index_file_paths() result
- Eliminates redundant directory path construction in create_index()
- Uses index_file.parent.mkdir() instead of separate directory iteration
- Ensures perfect consistency between creation, cleanup, and task targets

Author: rdebay-scality

buildchain/buildchain/targets/repository.py

@@ -280,10 +280,9 @@ def clean() -> None:
 
         def create_index() -> None:
             """Create empty index.html files in repository directories."""
-            for repository_directory in self._get_repository_directories():
+            for index_file in self._get_index_file_paths():
                 # Create directory if it doesn't exist, then create index.html
-                repository_directory.mkdir(parents=True, exist_ok=True)
-                index_file = repository_directory / self.INDEX_HTML_FILENAME
+                index_file.parent.mkdir(parents=True, exist_ok=True)
                 index_file.touch()
                 # Set readable permissions for nginx
                 index_file.chmod(0o644)