Duration returning as zero on Audio

## 🐛 Bug Report

When trying to retrieve the total duration of audio file it is returning 00:00:00

### Expected behaviour
Duration of the audio file to be returned

### Reproduction steps

var mediaItem = await CrossMediaManager.Current.Play(audioFile);
var duration = mediaItem.Duration;
await DisplayAlert("info", duration.ToString(), "OK");

### Configuration

**Version:** 1.1.1

**Platform:**
Xamarin.Forms

Start with the CrossMediaManager.Current.Play entry point and reproduce the reported Xamarin.Forms case using the steps in the issue. Trace how mediaItem.Duration is obtained for audio, then verify that it reports the file's actual duration rather than 00:00:00.

Written by the indexing model from the issue text.