UI shows rebalance to change mode from 2.0 to 3.0 after all nodes in cluster converted to 3.0

Install couchbase server 2.0.0 on 2 nodes 148 and 149
Create cluster of 2 nodes
Create 3 buckets: default, sasl and standard bucket.
No doc or view created
Load 1K items to each bucket
Install couchbase server 3.0.0-990 in to node 150 and 151
Add node 150 and 151 to 2.0 cluster.
3.0 node takes over master. Passed
Rebalance in 2 3.0 nodes into cluster. Passed
Remove 2 2.0 nodes out of cluster. Failed even thought the log saying rebalance successful.
1 3.0 node was kicked out of cluster and become pending node at the end of rebalance. Filed bug MB-11774 as I could reproduce it in centos cluster.
Rebalance again to rebalane pending node. Passed
When rebalance is done and all nodes in cluster become 3.0 version, UI shows cluster doing one more rebalance to change mode from 2.0 to 3.0