Following up on r1615541, tweak the naming of the introduced helper
function and its arguments.

* subversion/tests/cmdline/svnadmin_tests.py
  (write_sharded_format): Rename this ...
  (patch_format): ...into this.  Also tweak the argument name, because
    'shards' is ambiguous (if not entirely incorrect to use).
  (hotcopy_incremental_packed, verify_packed, fsfs_hotcopy_progress): Update
    these callers.  In order to make things a bit clearer, start using named
    arguments.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1618237 13f79535-47bb-0310-9956-ffa450edef68