lightnvm: put blks when luns configure failed

Put the allocated blocks back to the free list
when the luns configure failed, to make these
blocks useable to others.

Signed-off-by: Wenwei Tao <ww.tao0320@gmail.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>