Fix #137044 by prompting for a password if *none* is provided for ftp.
* bzrlib/transport/ftp.py: (FtpTransport._create_connection): The fix: the test was inverted. (_setup_medusa.test_authorizer.__init__): One user can be secured by verifying his password. (_setup_medusa.test_authorizer.authorize): Check the password if a secured user have been declared. Let the doors wide open otherwise (as before :-/).
* bzrlib/tests/test_ftp_transport.py: (TestFTPServer.test_basic_exists): New class for UI related tests.