Merge r1516271 from trunk:

 * r1516271
   svnwcsub: Fix creation of pid files.
   Justification:
     Security issue.
   Votes:
     +1: breser, danielsh


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1516547 13f79535-47bb-0310-9956-ffa450edef68