ui: ensure VNC websockets server checks the ACL if requested

If the x509verify option is requested, the VNC websockets server
was failing to validate that the websockets client provided an
x509 certificate matching the ACL rules.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
