bpo-37400: Fix test_os.test_chown() (GH-14374)


Use os.getgroups() rather than grp.getgrall() to get groups.
Rename also the test to test_chown_gid().
(cherry picked from commit d7c87d982d4ec4ba201bcee14324ae5e0e90581f)

Co-authored-by: Victor Stinner <vstinner@redhat.com>
2 files changed