Use 'new' rather than 'unknown' when starting transaction

'unknown' has a negative connotation for a case that's totally
normal so refer to it as 'new' so it doesn't sound like a problem.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/src/gsm_04_11.c b/openbsc/src/gsm_04_11.c
index 38f585b..31526e9 100644
--- a/openbsc/src/gsm_04_11.c
+++ b/openbsc/src/gsm_04_11.c
@@ -910,7 +910,7 @@
 	trans = trans_find_by_id(lchan->subscr, GSM48_PDISC_SMS,
 				 transaction_id);
 	if (!trans) {
-		DEBUGPC(DSMS, "(unknown) ");
+		DEBUGPC(DSMS, "(new) ");
 		trans = trans_alloc(lchan->subscr, GSM48_PDISC_SMS,
 				    transaction_id, new_callref++);
 		if (!trans) {