Avg throughput (ops/sec) of Magma YCSB workload A test dropped from 508K to 109K

Avg Throughput (ops/sec), Workload A, 3 nodes, 1 bucket x 1.5B x 1KB, 1% Resident Ratio, Magma

There are 14 magma changes between these two builds.

http://changelog.build.couchbase.com/?product=couchbase-server&fromVersion=7.6.0&fromBuild=1363&toVersion=7.6.0&toBuild=1419&f_asterixdb=off&f_backup=off&f_build=off&f_cbas-core=off&f_cbbs=off&f_cbft=off&f_cbftx=off&f_cbgt=off&f_couchbase-cli=off&f_eventing=off&f_eventing-ee=off&f_forestdb=off&f_gomemcached=off&f_goxdcr=off&f_indexing=off&f_kv_engine=off&f_magma=on&f_n1fty=off&f_ns_server=off&f_plasma=off&f_platform=off&f_product-metadata=off&f_query=off&f_query-ee=off&f_testrunner=off&f_tlm=off&f_voltron=off