hnbgw: use OSMO_STRLCPY_ARRAY() instead of open coding it

Change-Id: I4c539168597187408c31b906fd57844e0f165c9b
diff --git a/src/hnbgw.c b/src/hnbgw.c
index f18d2b1..dd157d7 100644
--- a/src/hnbgw.c
+++ b/src/hnbgw.c
@@ -195,10 +195,9 @@
 		return NULL;
 
 	ue->hnb = hnb;
-	if (imsi) {
-		strncpy(ue->imsi, imsi, sizeof(ue->imsi));
-		ue->imsi[sizeof(ue->imsi)-1] = '\0';
-	} else
+	if (imsi)
+		OSMO_STRLCPY_ARRAY(ue->imsi, imsi);
+	else
 		ue->imsi[0] = '\0';
 	ue->tmsi = tmsi;
 	ue->context_id = get_next_ue_ctx_id(hnb->gw);