CBQE:0 Correct bucket size for dgm runs

Change-Id: Iac83b7de77c913af27f3b4ffb3c4eaaca9cec12a
Reviewed-on: http://review.couchbase.org/44336
Reviewed-by: Aruna Piravi <aruna@couchbase.com>
Tested-by: Aruna Piravi <aruna@couchbase.com>