Disable UpdateInfo plugin again

MaintenanceTool right now shows an error when it can't connect to
the servers ... Disable the plugin until this is resolved.

Task-number: QTIFW-431
Change-Id: I45a0a26512bdbd590d212e76cff510b45feeb6f2
Reviewed-by: Niels Weber <niels.weber@digia.com>
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>