lightnvm: put block back to gc list on its reclaim fail

lightnvm: put block back to gc list on its reclaim fail

BugLink: http://bugs.launchpad.net/bugs/1531539
We delete a block from the gc list before reclaim it, so
put it back to the list on its reclaim fail, otherwise
this block will not get reclaimed and be programmable
in the future.

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>
(cherry picked from commit d0ca798f960ad7d86f5186fe312c131d00563eb7)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>