[3.12] gh-108948: Skip test_tarfile.test_modes() on EFTYPE error (#109697) (#109698)

gh-108948: Skip test_tarfile.test_modes() on EFTYPE error (#109697)

On FreeBSD, regular users cannot set the sticky bit. Skip the test if
chmod() fails with EFTYPE error.

(cherry picked from commit 26e06ad617bb416201c769fea91cd33d544c6a1c)