Comment 4 for bug 1840788

Fix [1], being worked via related bug [2], resolve that bug but not this one, as can be seen from [3] where I've tested [1] against [4].

The _validate_websocket_upgrade bit succeeds, but the subsequent bit, _validate_rfb_negotiation, fails [5].

[1] https://review.opendev.org/#/c/674364/
[2] https://bugs.launchpad.net/tempest/+bug/1838777
[3] https://review.opendev.org/#/c/677798/1
[4] https://review.opendev.org/677479
[5] https://storage.gra1.cloud.ovh.net/v1/AUTH_dcaab5e32b234d56b626f72581e3644c/logs_98/677798/1/check/tempest-full/604808b/testr_results.html.gz