On the 1.7.x branch, merge r1483781.

* r1483781
  Fix FSFS repository corruption on power or network disk failure on Windows:
  http://svn.haxx.se/dev/archive-2013-05/0245.shtml
  Justification:
    Repository corruption. Regression from 1.6.x
  Votes:
    +1: ivan, blair, stsp


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.7.x@1485189 13f79535-47bb-0310-9956-ffa450edef68