Iterate Maintenancetool updates for all versions counting down from latest

Related to SDKtool split, it would be good to test older versions of Maintenancetool update.

https://ci-files02-hki.ci.qt.io/packages/jenkins/archive/ifw/enterprise/unifiedqt/ has all versions all the way back to version 3.1.1.

Test logic:

1. Download OS spesific online installer from https://ci-files02-hki.ci.qt.io/packages/jenkins/archive/ifw/enterprise/unifiedqt/4.5.0/ 
2. start online installer, enter creds, press next. In 'Setup Qt' -screen, click settings in lower left side of window --> 

Click repositories, deselect "xxxx Maintenance Tool online repository"
3. navigate to component selection, deselect all --> install.
4. after install, run Maintenancetool update, update all incoming updates --> verify content --> install Qt Creator, Qt --> build one example --> verify.

Drop version one step --> 4.4.0 --> Rinse and repeat until 3.1.1/fail happens.