Refactor mobilenetwork.js code (bug 1056088)

https://bugzilla.mozilla.org/show_bug.cgi?id=1056088

Since we are becoming a real packaged app, it's time to clean-up that code.
I think this will always be `true`. If we want this check it would need to be `if (lastNetwork.mcc && lastNetwork.mnc)` or update `mccify` to return `false` as expected.