dm thin: resume even if in FAIL mode

If a thinpool set fail_io while suspending, resume will fail with:
 device-mapper: resume ioctl on vg-thinpool  failed: Invalid argument

The thin-pool also can't be removed if an in-flight bio is in the
deferred list.

This can be easily reproduced using:

  echo "offline" > /sys/block/sda/device/state
  dd if=/dev/zero of=/dev/mapper/thin bs=4K count=1
  dmsetup suspend /dev/mapper/pool
  mkfs.ext4 /dev/mapper/thin
  dmsetup resume /dev/mapper/pool

The root cause is maybe_resize_data_dev() will check fail_io and return
error before called dm_resume.

Fix this by adding FAIL mode check at the end of pool_preresume().

Cc: stable@vger.kernel.org
Fixes: da105ed5

 ("dm thin metadata: introduce dm_pool_abort_metadata")
Signed-off-by: Luo Meng <luomeng12@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>