Fix possible non-null-terminated buffer

Change-Id: I22100c260856991b9a836135b3650e5b8c5449ca
Fixes: Coverity CID 57623
diff --git a/openbsc/src/libmsc/vty_interface_layer3.c b/openbsc/src/libmsc/vty_interface_layer3.c
index 6f0006c..0b360b8 100644
--- a/openbsc/src/libmsc/vty_interface_layer3.c
+++ b/openbsc/src/libmsc/vty_interface_layer3.c
@@ -568,6 +568,7 @@
 	}
 
 	strncpy(subscr->name, name, sizeof(subscr->name));
+	subscr->name[sizeof(subscr->name)-1] = '\0';
 	talloc_free(name);
 	db_sync_subscriber(subscr);