vty: Everything <= CONFIG_NODE is not a child of config

The method should be renamed to is child of config node
as it was comparing if vty->node > CONFIG_NODE. This is
fixing an assert in go_to_parent as we tried to find a
parent for the CONFIG_NODE.
diff --git a/src/vty/command.c b/src/vty/command.c
index c55e164..7525df6 100644
--- a/src/vty/command.c
+++ b/src/vty/command.c
@@ -141,9 +141,9 @@
 
 static int is_config(struct vty *vty)
 {
-	if (vty->node < CONFIG_NODE)
+	if (vty->node <= CONFIG_NODE)
 		return 0;
-	else if (vty->node >= CONFIG_NODE && vty->node < _LAST_OSMOVTY_NODE)
+	else if (vty->node > CONFIG_NODE && vty->node < _LAST_OSMOVTY_NODE)
 		return 1;
 	else if (host.app_info->is_config_node)
 		return host.app_info->is_config_node(vty, vty->node);