declarativeqt: remove the bus watcher when we get an error or EOS
declarativeqt: remove the bus watcher when we get an error or EOS

We don't really need to keep it as we will stop playback anyway.
We also don't reuse the component so we are fine removing the watch

mlehtima/cameraplus,alinelena/cameraplus,foolab/cameraplus,mer-hybris-kis3/cameraplus,alinelena/cameraplus,foolab/cameraplus,alinelena/cameraplus,mer-hybris-kis3/cameraplus,mlehtima/cameraplus,alinelena/cameraplus,foolab/cameraplus,mlehtima/cameraplus,mlehtima/cameraplus,mer-hybris-kis3/cameraplus,mer-hybris-kis3/cameraplus,foolab/cameraplus