Rebalancing with 5 buckets and 5 sasl buckets takes 20 minutes

Build: 4.0.0-1767

Command:
./testrunner -i ~/servers/mvvms.ini -t rebalance.rebalancein.RebalanceInTests.rebalance_in_with_ops,nodes_in=3,items=0,default_bucket=false,standard_buckets=5,sasl_buckets=5,get-logs=true,get-cbcollect-info=true

The rebalance portion of this test took 20 minutes:
2015-04-08 13:51:10 | INFO | MainProcess | Cluster_Thread | [rest_client.rebalance] rebalance params : password=password&ejectedNodes=&user=Administrator&knownNodes=ns_1%4010.1.2.35%2Cns_1%4010.1.2.30%2Cns_1%4010.1.2.32%2Cns_1%4010.1.2.34
2015-04-08 13:51:10 | INFO | MainProcess | Cluster_Thread | [rest_client.rebalance] rebalance operation started
2015-04-08 13:51:10 | INFO | MainProcess | Cluster_Thread | [rest_client._rebalance_progress] rebalance percentage : 0.00 %
2015-04-08 13:51:20 | INFO | MainProcess | Cluster_Thread | [rest_client._rebalance_progress] rebalance percentage : 0.60 %

...

2015-04-08 14:12:48 | INFO | MainProcess | Cluster_Thread | [rest_client._rebalance_progress] rebalance percentage : 99.68 %
2015-04-08 14:12:58 | INFO | MainProcess | Cluster_Thread | [task.check] rebalancing was completed with progress: 100% in 1308.07790804 sec

Note that if I did 1 bucket and 1 sasl bucket the rebalancing took 2 minutes so adding buckets appears to cause non-linear behavior.

Logs are attached.