CBQE-0 :: fix vbucket movement failure in rabalanceinout tests

Change-Id: Ib624ccd27dd9f7f2de4d850d2b67794a568c42b6
Reviewed-on: http://review.couchbase.org/40027
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: buildbot <build@couchbase.com>