Bug 1064491: Request per-app data usage after first requesting total data usage

There is a race condition here but your patch works almost perfect. Notice that `updateCharts()` **does not** return a promise, not even a _thenable_ and it is inside that function, inside an asynchronous call to `SimManager.requestDataSimIcc()` where you expand the model filling the `mobile.total` field. So, by the time you check if there is or is not total mobile data (`maybeRequestPerAppUsage()`), that field could have not been filled yet (what is the behavior I'm observing).