CBQE-0: rem unneeded ClusterOperationHelper.remove_and_rebalance

Change-Id: I9cc5c37aaefa05965f641e7e30f0fe71a17393f0
Reviewed-on: http://review.couchbase.org/27288
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>