Bug 1083159 - [Loop] Issues reported in Loop locales that need to be fixed before Localization teams starts working

Keep this line! `getRevokeDate` can return a `null` [1], that's why we have this double check (easy to reproduce if you change the date in your device). If the difference of time is 0 or negative, we must show 'Expired'.

[1]https://github.com/mozilla-b2g/firefoxos-loop-client/blob/master/js/utils.js#L52