Known issue: unsafe failover may not enable Rebalance button when some indexes/index partitions not available

MB-46725 in the case of unsafe failover that removes one or more indexer nodes from the cluster, the Rebalance button on the UI may not become enabled even though some indexes or index partitions are not available because the remaining indexer node(s) did not have any replicas of them.

The work-around is to issue a rebalance command via CLI:

couchbase-cli rebalance -c 127.0.0.1:8091 -u Administrator -p xxxxxx