lib: media_discoverer: don't listen to Started/Ended events
lib: media_discoverer: don't listen to Started/Ended events

These events are useless and are only triggered when calling vlc_sd_Start() and
vlc_sd_Stop().

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc