[BUG] [Zone Decommission] MetadataDiff is 0 when publishing cluster state for status update

[imRishN]

Describe the bug
While updating the decommission status, the cluster state update is not applied to non leader nodes, and the local state of the nodes doesn't receive the status update. The reason being, while executing the cluster state update for decommission status update, the same instance of metadata was being update causing the relative diff to be 0 for non leader nodes and hence, the leader though had the appropriate decommission status but rest of the nodes had a stale decommission state.

To Reproduce
Steps to reproduce the behavior:

1. Execute attribute decommission - curl -X PUT "localhost:9201/_cluster/decommission/awareness/zone/zone-2?pretty
2. Check the local cluster state of any node - curl -X GET "localhost:9202/_cluster/state?local&pretty"
3. Check the cluster level cluster state - curl -X GET "localhost:9202/_cluster/state?pretty"
4. The cluster state from (3) would have the latest updated the status but cluster state from (2) has status as INIT

Expected behavior
The latest cluster state and decommission status to be published to all nodes.

[imRishN]

Closing as PR is merged