md-cluster: introduce resync_info_get interface for sanity check

Since the resync region from suspend_info means one node
is reshaping this area, so the position of reshape_progress
should be included in the area.

Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>