CBQE-0: SanityTest hangs on warmupcluster.WarmUpClusterTest

it hangs when rebalance failed in setup

Change-Id: Ia0ecc2d5559bd524a927009f96a45327a94fec8a
Reviewed-on: http://review.couchbase.org/26372
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>