bug#11725: 24.1; confirm-nonexistent-file-or-buffer with after-completion value

[Szunti <szunti@gmail.com>]

Using the default value of "after-completion" of the variable
"confirm-nonexistent-file-or-buffer" never asks for confirmation.

I made a git bisect, the first bad commit is:

     commit 064b509639208159ca7c619bccf319aef7950146
     Author: Stefan Monnier <monnier@iro.umontreal.ca>
     Date: Mon Mar 12 00:10:59 2012 -0400

         * lisp/minibuffer.el (minibuffer-complete): Don't get confused 
when the
         function is run twice via different commands.
         (complete-with-action): Fix docstring.

Steps to reproduce after bad commit:

1) made two files in bash:
$ cd /tmp
$ touch almafa almacsutka

2) open emacs
C-x C-f /tmp/al[TAB][RET]

[TAB] completes to /tmp/alma, then after pressing [RET], a new file
called alma is open, instead of asking for confirmation.