This fixes potential bio leaks, in several error paths. Unfortunatelly
the device structure freeing is opencoded in many places and I missed
them when introducing the flush_bio.
Most of the time, devices get freed through call_rcu(..., free_device),
so it at least it's not that easy to hit the leak, but it's still
possible through the path that frees stale devices.
Fixes: e0ae99941423 ("btrfs: preallocate device flush bio") Reviewed-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>