Always use eth0 for xbmc

[Roy Terhaar]

@deHakkelaar and@Nachteule,

Thanks for the response, but my problem was a bit different I guess, because I am running Kodi on eth0, so basically I don't care if wlan0 is up or not before starting Kodi. However Kodi seems to always choose the last interface that's activated. I also noticed that sometimes it loses settings of the eth0 interface and uses the settings of the wlan0 instead (gateway configuration) which makes no sense.
But my workaround seems to be working most of the times...