It's useful to show the thumbnail as the player's backdrop when Video Autoplay is OFF, but it's a wasted fetch when it's ON because the videojs component will be blocking it.
Although it's the same image as the ClaimPreview, this one will be in full size, so a fetch will always happen.
Aside: videojs handles the backdrop for the audio and embed case, so this change won't affect those items.
```
<VideoJs
poster={isAudio || (embedded && !autoplayIfEmbedded) ? thumbnail : ''}
/>
```
Future: for "mobile + autoplay=OFF", we should consider using the optimized thumbnail. 6074 should help.
