When hotcopying non-shared repositories, checkpoint the progress after
every revision.  This is not strictly necessary and adds a performance
penalty but improves behavior if we re-run hotcopy after cancelling a
previous one.

* subversion/libsvn_fs_fs/hotcopy.c
  (hotcopy_body): Checkpoint "current" after each rev in nonshared reps
                  and give a detailed rationale.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1560723 13f79535-47bb-0310-9956-ffa450edef68