Follow-up to r1540044: fix the incremental case as well.

* subversion/libsvn_fs_fs/hotcopy.c
  (hotcopy_body): remove revprop files only if they have actually
                  been packed, i.e. if the repo format supports that

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1540417 13f79535-47bb-0310-9956-ffa450edef68