chan_sip: Send 408 on retransmit timeout instead of 603

(closes issue ASTERISK-20124)
Reported by: Walter Doekes
........

Merged revisions 371824 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 371825 from http://svn.asterisk.org/svn/asterisk/branches/10
........

Merged revisions 371845 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@371851 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -3928,7 +3928,7 @@ static int retrans_pkt(const void *data)
 				/* there is nothing left to do, mark the dialog as gone */
 				sip_alreadygone(pkt->owner);
 			}
-			ast_queue_hangup_with_cause(pkt->owner->owner, AST_CAUSE_PROTOCOL_ERROR);
+			ast_queue_hangup_with_cause(pkt->owner->owner, AST_CAUSE_NO_USER_RESPONSE);
 			ast_channel_unlock(pkt->owner->owner);
 		} else {
 			/* If no channel owner, destroy now */