Fix hotcopy code for pre-1.4 FSFS repositories.

* subversion/libsvn_fs_fs/hotcopy.c
  (hotcopy_update_current): Bump the revision number *before* trying
                            to read the new rev(s) from the target repo.
  (hotcopy_body): Prevent multiple, expensive max ID scans.

* subversion/tests/cmdline/svnadmin_tests.py
  (fsfs_hotcopy_old_non_empty): Should pass now.

Patch by: Evgeny Kotkov <evgeny.kotkov{_AT_}visualsvn.com>


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1561427 13f79535-47bb-0310-9956-ffa450edef68