Fix startup visibility bug

* lisp/org.el (org-cycle): Make sure resetting to startup visibility
works after another cycle command.

Gez writes:

> I have a query about the C-u C-u TAB command.  When I've just edited
> or used S-TAB (no matter which part of the global cycle it's on) C-u
> C-u TAB works as I would expect.  But if I've just used TAB, C-u C-u
> TAB cycles hrough -> CONTENTS -> SHOW ALL etc, even while the mini
> buffer displays "startup visibility plus VISIBILITY properties" at
> each stage of the cycle. C-u C-u TAB also cycles when it's repeated.
> I find it hard to keep track of whether it will cycle or not while I'm
> using it to view areas of the outline, so in effect, the only way I
> feel sure I can quickly return to my desired startup visibility is
> with S-TAB C-u C-u TAB, which is a lot of keystrokes! So my questions
> are - is this expected behaviour?  Can it be changed?

lisp/org.el

@@ -5814,6 +5814,7 @@ in special contexts.
       (cond
 
        ((equal arg '(16))
+	(setq last-command 'dummy)
 	(org-set-startup-visibility)
 	(message "Startup visibility, plus VISIBILITY properties"))