no more rtsp, fallback for livestream

tagesschau has removed the RTSP streams that were previously used for live streams. 

I've switched to using one of the other video formats, which is working fine on raspbmc. 
However, my Frodo on Mac OSX seems to choke on both the "m3u8_A" and "http_tab" live streams. 

In any case, at least this commit fixes the concrete issue raised in https://github.com/joerns/xbmc-plugin.video.tagesschau/issues/5