vty/vty.c: do not bind vty context to application's one

The 'vty_app_info' struct could be used by some applications to
provide its talloc context. In the future, it will facilitate
the implementation of talloc context introspection via VTY.

But the 'vty' talloc context, that contains lots of items
(memory chunks), is being bound to an application's one,
so it becomes hard to read the last.

Let's do not bind the 'vty' context automatically, until some
common talloc context export policy is implemented.

Change-Id: I9cb6ce9f24dbae400029e2d9f9c933fbfb16248f
diff --git a/src/vty/vty.c b/src/vty/vty.c
index bd0d2c3..3d9c0d6 100644
--- a/src/vty/vty.c
+++ b/src/vty/vty.c
@@ -1773,7 +1773,7 @@
 /* Install vty's own commands like `who' command. */
 void vty_init(struct vty_app_info *app_info)
 {
-	tall_vty_ctx = talloc_named_const(app_info->tall_ctx, 0, "vty");
+	tall_vty_ctx = talloc_named_const(NULL, 0, "vty");
 	tall_vty_vec_ctx = talloc_named_const(tall_vty_ctx, 0, "vty_vector");
 	tall_vty_cmd_ctx = talloc_named_const(tall_vty_ctx, 0, "vty_command");