[iOs] plugin configures AVAudioSession after AVAudioPlayer makes it active inside prepareToPlay

[RSATom]

According to AVAudioPlayer docs prepareToPlay activates audio session (in plugin it happens here). But plugin calls setCategory for AVAudioSession a little bit later, i.e. at wrong time.

[RSATom]

I found this issue while was trying to solve #306. I was trying to add withOptions:AVAudioSessionCategoryOptionMixWithOthers to https://github.com/apache/cordova-plugin-media/blob/master/src/ios/CDVSound.m#L374 but it was working only on second play...

[johannds]

It blows my mind that this isn't configurable inside this highly used plugin.