Fix issue 4448: hotcopy losing revprop files.

* subversion/libsvn_fs_fs/hotcopy.c
  (hotcopy_body): Only remove unpacked revprop files if the repository
   supports revprop packing.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1540044 13f79535-47bb-0310-9956-ffa450edef68