Display who ended the session in sip_audio_session.py

darcs-hash:20090212132324-58103-0035d7ace80e47ad56019166030c5fafdc22d803
Fixed log text when session ended

darcs-hash:20090213084254-58252-7bb7c7d80ab50678bfabd4b1f2ce3ee3c285ff57