Simplified fix avoiding changes to mysys:
  Use the MY_HOLD_ORIGINAL_MODES flag when calling my_copy(),
    this also stops it from attempting to chown() the file.
  Yes this behavior is a bit confusing....
  The only case this might change the behavior is if the destination file
    exists, but since we also use MY_DONT_OVERWRITE_FILE, it would fail
    in those cases anyway.