[VTY] Remove OpenBSC specific node-exit handling from src/vty

The idea is to move the VTY code into libosmocore at some point,
and for that we need to eliminate OpenBSC specifics from it
diff --git a/openbsc/src/vty/vty.c b/openbsc/src/vty/vty.c
index 0806856..986902a 100644
--- a/openbsc/src/vty/vty.c
+++ b/openbsc/src/vty/vty.c
@@ -731,6 +731,8 @@
 static void vty_down_level(struct vty *vty)
 {
 	vty_out(vty, "%s", VTY_NEWLINE);
+	/* FIXME: we need to call the exit function of the specific node
+	 * in question, not this generic one that doesn't know all nodes */
 	(*config_exit_cmd.func) (NULL, vty, 0, NULL);
 	vty_prompt(vty);
 	vty->cp = 0;
@@ -741,6 +743,8 @@
 {
 	vty_out(vty, "%s", VTY_NEWLINE);
 
+	/* FIXME: we need to call the exit function of the specific node
+	 * in question, not this generic one that doesn't know all nodes */
 	switch (vty->node) {
 	case VIEW_NODE:
 	case ENABLE_NODE: