If --set-depth isn't passed to an update, don't change the depth.

If --set-depth isn't passed to an update, don't change the depth.

We do this by reverting r28904, which removed an unused baton, and
instead we use the baton.

* subversion/libsvn_wc/update_editor.c
  (struct edit_baton): Add depth_is_sticky member.
  (complete_directory): Only do depth upgrade if depth is sticky.
  (make_editor): Populate member.

* subversion/tests/cmdline/depth_tests.py
  (test_list): depth_empty_update_bypass_single_file now passes.

git-svn-id: http://svn.collab.net/repos/svn/trunk@28907 612f8ebc-c883-4be0-9ee0-a4e9ef946e3a