[Core] Only fsync the directory if GNU constant exists

* Doesn't exist on Windows.

deluge/core/torrentmanager.py

@@ -756,6 +756,7 @@ class TorrentManager(component.Component):
                     os.rename(filepath_bak, filepath)
             else:
                 # Sync the rename operations for the directory
+                if hasattr(os, 'O_DIRECTORY'):
                     dirfd = os.open(os.path.dirname(filepath), os.O_DIRECTORY)
                     os.fsync(dirfd)
                     os.close(dirfd)