Restore window configuration after Ediff

[PJ Weisberg <pj@irregularexpressions.net>]

I'm not 100% sure if this is a bug or if I'm trying to do something I
should try to do.  I'm trying to call ediff-buffers and then use a
hook to restore the frame to its original state after Ediff is done.
Here's some sample code:

======================================================================
(defvar saved-configuration nil)

(defun do-ediff()
  (interactive)
  (add-hook 'ediff-quit-hook 'do-ediff-cleanup)
  (setq saved-configuration (current-window-configuration))
  (ediff-buffers "*scratch*" "*scratch*"))

(defun do-ediff-cleanup()
  (set-window-configuration saved-configuration)
  (remove-hook 'ediff-quit-hook 'do-ediff-cleanup))
======================================================================

The problem is that after I quit ediff, the ediff control frame
doesn't always disappear.

I get the behavior I want if I use ediff-after-quit-hook-internal
instead of ediff-quit-hook, but the "internal" part of that name tells
me that's a bad idea.

Is there a better way to accomplish what I'm trying to do?

-PJ