Load failures now have a Chromium side timeout of 10s so we need to wait
longer than that. Additionally error-pages no longer have descriptive
titles, so we can not rely on that in our tests any longer.

Change-Id: I33ac8b9f1247403eb214f7260267edb887fe10d0
Reviewed-by: Michal Klocek <michal.klocek@qt.io>