Fix DAG cache locking inefficiency: Due to a coding snafu, it create
many locks for the same pool.

* subversion/libsvn_fs_fs/tree.c
  (lock_cache): Actually traverse the list of locks.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1590384 13f79535-47bb-0310-9956-ffa450edef68