Did this quite a while back, but haven't tested yet.

Changes to make a client even more passive when there are blocks in
flight (requested by someone else) that they can use. The goal here
is to keep a late joining client from making requests for chunks that
all the others have already seen. This is not a big problem in the
default case where clients randomize the order of chunks they request,
but when they are making sequential requests it can be a problem.