Set a default Config.extended_filesystem_attributes.

diffoscope/config.py

@@ -63,6 +63,7 @@ class Config:
         self.exclude_directory_metadata = "no"
         self.acl = True
         self.xattr = True
+        self.extended_filesystem_attributes = False
         self.compute_visual_diffs = False
         self.max_container_depth = 50
         self.use_dbgsym = "auto"