Modified registration related logging in sip_audio_session

Ignore-this: bc7638928dd9d0d72bfa7d408ae3eff5

darcs-hash:20090406203900-1e3d8-9092a4f04670041bf8b40e4d8d3ecef23a02aeec
Added registration related logging in sip_message

Ignore-this: 321a0cf3f271829e403bd0199accbfd3

darcs-hash:20090406210717-1e3d8-735d03f524b075598ee2a62436e44c78e427e964