Follow-up to 1448810: fix canonicalization check for paths containing
a single character and update two indirect callers of open_path.

* subversion/libsvn_fs_fs/tree.c
  (fs_copy,
   fs_revision_link): ensure canonical path parameters

* subversion/libsvn_fs_util/fs-util.c
  (is_canonical_abspath): fix canonicalization check for single-char paths

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1448820 13f79535-47bb-0310-9956-ffa450edef68