Refactored sip_audio_session script

Ignore-this: 9e5a22d9c4b4ce74406d281b69feaa9d

darcs-hash:20090720160523-1e3d8-ee92a831453b33ace621461c7ca20e8d7eaf8692
Removed playback_dtmf setting from scripts

Ignore-this: 4299f9ecb769d40c1e831be0eb1e0a39

darcs-hash:20090720160747-1e3d8-e2ff6774a15e383c27b1f83ed5a48d78ac30f36a