Insignificant flag is added for two targets. RedHat 7.6
will be kept as parallel until insignificant flag can be
removed from CentOS
Task-number: QTQAINFRA-2760
Task-number: QTQAINFRA-3065
Change-Id: If124600309644e6a066805cd728bf12862006a21
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@qt.io>