nitb: Make the last change configurable

Introduce a NITB node and add the subscriber creation as
config name in there.
diff --git a/openbsc/src/libcommon/common_vty.c b/openbsc/src/libcommon/common_vty.c
index 3f8f16f..186fbe0 100644
--- a/openbsc/src/libcommon/common_vty.c
+++ b/openbsc/src/libcommon/common_vty.c
@@ -106,6 +106,7 @@
 	case BSC_NODE:
 	case MSC_NODE:
 	case MNCC_INT_NODE:
+	case NITB_NODE:
 	default:
 		if (bsc_vty_is_config_node(vty, vty->node))
 			vty->node = CONFIG_NODE;