Bug 1096824 - [Loop] Sign up requests might be unauthorized due to assertions expired

See bug https://bugzilla.mozilla.org/show_bug.cgi?id=1096824. Action happens at https://github.com/jaoo/firefoxos-loop-client/tree/1096824.
> https://github.com/mozilla-b2g/firefoxos-loop-client/blob/master/app/js/helpers/account_helper.js#L230
> 
> I was referring to this signIn.

Note we check for 401/110 errors at AccountHelper.signIn() function which means that even when _onloginerror gets called the check was made.