Introduce a new option abort_on_full, default to false. Then
we can get -ENOSPC when the pool is full, or reaches quota.

[ Don't show abort_on_full in /proc/mounts. ]
Signed-off-by: NDongsheng Yang <dongsheng.yang@easystack.cn>
Reviewed-by: NIlya Dryomov <idryomov@gmail.com>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>