For cluster scenario, add device is different with native raid.
When a node issues adds a device, then the node will broadcast
a message with UUID to other nodes in the cluster. If receiving
node can find the device with the specific UUID, it must confirm
the device, otherwise reports it is missing.
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>