Drop in workload SK throughput

Build 5.5.0-2556
Observed drop in SOE workload sk throughput from 84K(5.5.0-2520) to 40K(5.5.0-2556).
Results available on showfast- http://showfast.sc.couchbase.com/#/timeline/Linux/n1ql/soe/all
Discussed this in weekly performance meeting.

Job- http://perf.jenkins.couchbase.com/job/hebe/1149
Logs-
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-hebe-1149/172.23.100.190.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-hebe-1149/172.23.100.191.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-hebe-1149/172.23.100.192.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-hebe-1149/172.23.100.193.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-hebe-1149/172.23.100.204.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-hebe-1149/172.23.100.205.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-hebe-1149/172.23.100.206.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-hebe-1149/172.23.100.207.zip