Follow-up to r1645567.

* subversion/libsvn_fs_fs/tree.c
  (open_path): We always return DAG nodes locked in the cached.
               Be consistent with that in the short-cut case.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1648230 13f79535-47bb-0310-9956-ffa450edef68