Fixed #18019 -- Use threaded runserver only when database supports it.

        # a strange error -- it causes this handle() method to be called

        # multiple times.

        shutdown_message = '\nServer stopped.\nNote that the test database, %r, has not been deleted. You can explore it on your own.' % db_name

        call_command('runserver', addrport=addrport, shutdown_message=shutdown_message, use_reloader=False, use_ipv6=options['use_ipv6'])

        use_threading = connection.features.test_db_allows_multiple_connections

        call_command('runserver',

            addrport=addrport,

            shutdown_message=shutdown_message,

            use_reloader=False,

            use_ipv6=options['use_ipv6'],

            use_threading=use_threading

        )