Merge the r1512300 group from trunk:

 * r1512300, r1512301
   Clean up unpacked revprops in 'svnadmin hotcopy --incremental'
   Justification:
     Although keeping the unpacked revprop files should not do
     harm, it still results in the target repo being different
     from the source.  Also, it wastes disc space.
   Notes:
     r1512300 is merely a test case update to reproduce the problem.
   Votes:
     +1: stefan2, breser, rhuijben


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1520723 13f79535-47bb-0310-9956-ffa450edef68