Code review comment for lp:~lifeless/bzr/bug-395556

Fix dirstate.set_state_from_inventory to have a more stable
old_iterator, fixing rename problems in new trees. (Robert Collins, bug
395556)

I've removed some tests that helped to diagnose the problem but had
nothing to do with where or how it was occuring; I don't think they add
value to the test environment - the particular way they tickled the bug,
though interesting, is not demonstrating an interface problem, and is a
particularly expensive way of showing that lower levels aren't broken.

-Rob