Test maintenance tool update

Add the following case to the Installer smoke test suite:

Lets assume that current production maintenance tool and Qt installer versions are 4.8.0, and testable Qt installer and maintenance tool versions are 4.8.1

1. Take version 4.8.0 of Qt Installer and install without --at <maintenancetool_preview>
2. Verify that version 4.8.0 of maintenancetool is installed
3. Run update with --at <maintenancetool_preview>

 - for example <installer> update --at <maintenancetool_preview>

example: suites/shared/defines_ifw.py mt_tool_linux_x64 contains the url:s

4. Verify that maintenancetool version is updated to 4.8.1

Maintenancetool --version 

should output 4.8.1