Cannot disable manual nameserver configuration in Settings app

I noticed during testing of the libqtappfw rework that if a nameserver is configured in the wired network configuration in the Settings app, it is not disabled if the manual configuration is then disabled again in the dialog.  It sort of looks like the app QML code isn't actually calling down into the libqtappfw API to do so when this happens, so some poking around will be required to get it to do so and vet that the Network::configureNameServer method in libqtappfw does the correct thing (it's not immediately obvious it does even in the old code in Lamprey).