md-cluster: append some actions when change bitmap from clustered to none

For clustered raid, we need to do extra actions when change
bitmap to none.

1. check if all the bitmap lock could be get or not, if yes then
   we can continue the change since cluster raid is only active
   in current node. Otherwise return fail and unlock the related
   bitmap locks
2. set nodes to 0 and then leave cluster environment.
3. release other nodes's bitmap lock.

Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>