CBQE-0 :: add tests for active resident ratio and dgm, and fix logic to increase frequency for intra-cluster check pointing

Change-Id: I84c353b6248b9a0e339ece834a187c0179e1aad9
Reviewed-on: http://review.couchbase.org/40196
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: buildbot <build@couchbase.com>