Partially revert cbe41f266d7cc846285dc99164297cafdab667a0

It broke AirPlay with iOS 7 beta 3, the iPhone requiring a FairPlay authentication mechanism to connect
Fix deadlock should error occurs during stream constructor.

Lock wasn't released
Create AirPlay instance before RAOP one

This seems to help with iOS 7 otherwise thinking we only support audio
Fix occasional crash in AirPlay

MythCoreContext::WaitUntilSignals is called within the handling of a TcpSocket::read() event. If while we wait for playback to start, we receive another TcpSocket::read() signal, QEventLoop crashes; it doesn't like being re-entrant
Dismiss photo being currently displayed when video is about to start.

Create the notification on demand when a photo is about to be displayed so we can discard it later.

There's still something not quite right when transitioning between photos and videos. The iPhone tends to disconnect the session. I suspect the delay we take in providing playback feedback to be the cause