dm cache: Fix ABBA deadlock between shrink_slab and dm_cache_metadata_abort

Same ABBA deadlock pattern fixed in commit 4b60f452ec51 ("dm thin: Fix
ABBA deadlock between shrink_slab and dm_pool_abort_metadata") to
DM-cache's metadata.

Reported-by: Zhihao Cheng <chengzhihao1@huawei.com>
Cc: stable@vger.kernel.org
Fixes: 028ae9f7

 ("dm cache: add fail io mode and needs_check flag")
Signed-off-by: Mike Snitzer <snitzer@kernel.org>