Windows don't allow insecure guest login anymore by default. It need
to be enabled through Group Policy restrictions
Pick-to: 5.15
Pick-to: 5.12
Task-number: QTQAINFRA-3974
Change-Id: I5fd918882c51c01985cd4c1b9f9ed4dec62e07dd
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@qt.io>