lei q: eliminate $not_done temporary git dir hack

lei q: eliminate $not_done temporary git dir hack

Another step towards simplifying lei internals.

None of our current uses of ->wq_do involve FD passing, and the
plan is only rely on FD passing between lei-daemon and lei(1).
Internally, it ought to be possible for lei-daemon internal bits
to be ordered properly to not need FD passing.