core: fix parent/master confusion in some argument names

It's the parent, not the master, that we care about here.

src/NetworkManagerUtils.c

@@ -1028,8 +1028,8 @@ nm_utils_is_uuid (const char *str)
 }
 
 char *
-nm_utils_new_vlan_name (const char *master_iface, guint32 vlan_id)
+nm_utils_new_vlan_name (const char *parent_iface, guint32 vlan_id)
 {
-	return g_strdup_printf ("%s.%d", master_iface, vlan_id);
+	return g_strdup_printf ("%s.%d", parent_iface, vlan_id);
 }