CBQE-0: Fix rebalance and failover tests in UI

Change-Id: If936b389d818e15f35f1d0713b210040bd9ed2d4
Reviewed-on: http://review.couchbase.org/41604
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Meenakshi Goel <meenakshi.goel@globallogic.com>
Tested-by: Meenakshi Goel <meenakshi.goel@globallogic.com>