Added reason string to data for SCSessionDidFail notification

darcs-hash:20090212130908-58103-bf8c35526b0a285c47cb2e473bdbe5a550a1139f
Print session failure reason in sip_audio_session.py

darcs-hash:20090212130941-58103-c9c7f6ce6a6fc57c72ed316f037a43be8cf1d1d5