REST API - On Delta Recovery failure messages are not informative

You can repro this by doing the following

1. Create a 4 node cluster
2. Add default bucket with 100K items
3. Hard Failover a node and mark it for delta recovery
4. using CLI add a node and rebalance

Rebalance fails since delta recovery cannot be done in the above scenario. However, the message is not informative

Message as seen by running cli command::

ERROR: unable to rebalance cluster (400) Bad Request

[root@palm-10307 bin]#

The above message is what the REST API returns without giving information the scenario which fails the rebalance. In the UI this is a different message which tells us that we were trying to rebalance-in/out/swap which led to the failure.