Default to no jitter buffer on IAX2

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@1574 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configs/iax.conf.sample

@@ -42,7 +42,7 @@ disallow=lpc10			; Icky sound quality...  Mr. Roboto.
 ; excess jitter buffer, which if exceeded, causes the jitter buffer to
 ; slowly shrink in order to improve latency.
 ;
-;jitterbuffer=no
+jitterbuffer=no
 ;dropcount=3
 ;maxjitterbuffer=500
 ;maxexccessbuffer=100