AttributeError: 'TestUIFactory' object has no attribute 'tick'

Split out from bug 398668: many tests fail like this:

  File "/home/mbp/bzr/398668-2a-default/bzrlib/repofmt/groupcompress_repo.py", line 831, in fileids_altered_by_revision_ids
    pb=pb):
  File "/home/mbp/bzr/398668-2a-default/bzrlib/chk_map.py", line 1606, in process
    for record in self._read_all_roots():
  File "/home/mbp/bzr/398668-2a-default/bzrlib/chk_map.py", line 1519, in _read_all_roots
    old_chks_to_enqueue = self._read_old_roots()
  File "/home/mbp/bzr/398668-2a-default/bzrlib/chk_map.py", line 1479, in _read_old_roots
    self._read_nodes_from_store(self._old_root_keys):
  File "/home/mbp/bzr/398668-2a-default/bzrlib/chk_map.py", line 1459, in _read_nodes_from_store
    self._pb.tick()
AttributeError: 'TestUIFactory' object has no attribute 'tick'

This is probably fallout from my previous changes to the TestUIFactory...