  FILE -- This July 13, 2011, photo made available on the International Security Assistance Force's Flickr website shows the former Commander of International Security Assistance Force and U.S. Forces-Afghanistan Gen. Davis Petraeus, left, shaking hands with Paula Broadwell, co-author of  &quot;All In: The Education of General David Petraeus.&quot;  The Justice Department is dropping its investigation of David Petraeus' mistress, Paula Broadwell, into whether she stalked a romantic rival online.  (AP Photo/ISAF)  