Avoid starting playback if sending the app to the background while the player is preparing (if no background playback possible)

[defagos]

As reported by one of our teams, playback sometimes can occur in the background.

A possible reason could be that If the application is sent to the background while the player is still preparing (can be simulated with the network link conditioner), the completion handler will be called when the player is ready, at which point a call to -play from this handler might start playback in background.

While this is perfectly acceptable for audio or for video background playback if allowed, this should not occur if background behavior detaches the view (in which case we should probably pause the playback to simulate the associated effect).

[defagos]

As for SRG Media Player, I could not reproduce this behavior with Letterbox demo. Maybe the truth is somewhere else.