Throughput regressed for hot workload 20% RR

Test: 1 bucket x 250M. single 2i index. 20K KV ops/sec. hot workload. 20% Resident. PLASMA

Test Run: http://perf.jenkins.couchbase.com/job/secondary-plasma-dgm/6320/consoleFull 

cbmonitor: http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=nyx_720-5081_apply_scanworkload_1956&snapshot=nyx_720-5151_apply_scanworkload_e281 

Change logs: http://changelog.build.couchbase.com/?product=couchbase-server&fromVersion=7.2.0&fromBuild=5081&toVersion=7.2.0&toBuild=5151&f_asterixdb=off&f_backup=off&f_cbas=off&f_cbas-core=off&f_cbbs=off&f_cbft=off&f_cbftx=off&f_cbgt=off&f_couchbase-cli=off&f_couchdb=off&f_eventing=off&f_eventing-ee=off&f_golang=off&f_gomemcached=off&f_goxdcr=off&f_indexing=on&f_kv_engine=off&f_magma=off&f_n1fty=off&f_ns_server=off&f_plasma=on&f_platform=off&f_product-texts=off&f_query=off&f_query-ee=off&f_testrunner=off&f_vbmap=off&f_voltron=off