Timeout in the maintenance tool

Qt Installer does not timeout, if the underlying network layer (QNetworkAccessManager) does not report any error about the timeout.

This causes problems that the installer gets suspended during the installation and the only way to proceed is to re-start. 

If we had a timeout in the installer, the re-start could be automatic.

The timeout duration should be adjustable or even disabled. Someone could just move the laptop to another network and continue installation there.