iOS AutoPlay Shows Previous Video

## 🐛 Bug Report

On iOS, with AutoPlay true, calling Play( ) after a video has previously been played, will show the last frame from the previous video until buffering on the new video is complete and play begins. This makes it momentarily look like the wrong video is being played, and is very confusing for the user.

### Expected behavior

VideoView should be blank during initial buffering.

### Reproduction steps

100% reproducible. Turn AutoPlay on. Play a video. Stop it. Then play a second video and notice the previous video is still shown during buffering.

### Configuration

**Version:**
MediaManager: 0.9.7
Xamarin Forms: 4.7.0
iOS: 13.5

**Platform:**
- [ ] :iphone: iOS
- [ ] :robot: Android
- [ ] :checkered_flag: WPF
- [ ] :earth_americas: UWP
- [ ] :apple: MacOS
- [ ] :tv: tvOS
- [X] :monkey: Xamarin.Forms

Reproduce the issue on iOS with Xamarin.Forms and AutoPlay enabled by playing, stopping, and then starting a second video. Inspect the VideoView buffering and rendering lifecycle; done means the previous video's frame is cleared and the view remains blank until the new video begins playing.

Written by the indexing model from the issue text.