bpo-31233: socketserver.ThreadingMixIn.server_close() (#3523)

socketserver.ThreadingMixIn now keeps a list of non-daemonic threads
to wait until all these threads complete in server_close().

Reenable test_logging skipped tests.

Fix SocketHandlerTest.tearDown(): close the socket handler before
stopping the server, so the server can join threads.
3 files changed