md-cluster: remove the unused sb_lock

The sb_lock is not used anywhere, so let's remove it.

Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>
1 file changed