lightnvm: move responsibility for bad blk mgmt to target

We move the responsibility of managing the persistent bad block table to
the target. The target may choose to mark a block bad or retry writing
to it. Never the less, it should be the target that makes the decision
and not the media manager.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>