CBQE-2320 :: Add more tests for graceful failover with dynamic nodes

Change-Id: I518a3e18c92bee48ec29f684cbe449790e96081d
Reviewed-on: http://review.couchbase.org/39290
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Parag Agarwal <agarwal.parag@gmail.com>
Tested-by: Parag Agarwal <agarwal.parag@gmail.com>