high dcp_replica_items_remaining in Magma YCSB run

We ran the Magma YCSB DP test on the nvme cluster. Both runs are using the same build (1006.5.1-1128) and the same test configure. 

DP: http://perf.jenkins.couchbase.com/job/rhea-ycsb/856/

Logs:

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-rhea-ycsb-856/172.23.97.25.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-rhea-ycsb-856/172.23.97.26.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-rhea-ycsb-856/172.23.97.29.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-rhea-ycsb-856/172.23.97.30.zip

nvme: http://perf.jenkins.couchbase.com/job/magma-nvme-ycsb/185/

Logs:

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-magma-nvme-ycsb-185/172.23.100.135.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-magma-nvme-ycsb-185/172.23.100.136.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-magma-nvme-ycsb-185/172.23.100.137.zip

https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-magma-nvme-ycsb-185/172.23.100.138.zip

Compared to the DP run, the new run on the nvme cluster has lower performance. The nvme cluster has more CPU cores and higher CPU clock so it should have better performance.

When we compare these two runs, we see that the nvme run has lower resident ratio and much higher dcp_replica_items_remaining.

http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=rhea_100651-1128_access_1b28&snapshot=magma-nvme_100651-1128_access_08fc