sip_session2: removed useless code

darcs-hash:20090422090249-b2873-5f5418cdcf8c0026066f28c03e5f01330e76b5ba
fix GreenAudioStream.end(); add new state 'ENDING' to AudioStream

darcs-hash:20090422095340-b2873-e78106ce39056de323dcc186f940c74ffdf7ea8e