Resolve LiveTV vs. recording conflicts

This should help to resolve LiveTV conflicts. (https://github.com/fetzerch/xbmc-pvr-addons/issues/85)

Scheduled recordings will hang in MythTV if ASK_RECORDING is ignored.
Correct responses are either CANCEL_NEXT_RECORDING or stopping playback.

For now just stop the LiveTV recorder. (This will cause the player to hang but there's no API call to properly stop)
PVR extension is most likely needed to stop the player correctly.

See MythTV: libs/libmythtv/tv_play.cpp: TV::AskAllowRecording

@janbar: Any doubts on this quick fix? I work on correctly resolving it (by a dialog or setting) later.