Follow-up to r1527217: improve code readability. No functional change.

* subversion/libsvn_fs_fs/transaction.c
  (write_final_changed_path_info): formatting fix; use utility function

Suggested by: ivan

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1532893 13f79535-47bb-0310-9956-ffa450edef68