Fixes Issue #14992: os.makedirs(path, exist_ok=True) would raise an OSError

Fixes Issue #14992: os.makedirs(path, exist_ok=True) would raise an OSError
when the path existed and had the S_ISGID mode bit set when it was not
explicitly asked for.  This is no longer an exception as mkdir cannot control
if the OS sets that bit for it or not.