pillowfight throughput drop after 3.0.0-alpha.5 for r=1 p=0

Some of out pillowfight durability test were running with 3.0.0-alpha.5 and recently I began work to update these tests to run with libcouchbase 3.0.0. For one scenario, replicate_to=1 persist_to=0, we are seeing a 97% drop in throughput. 

Original test with 3.0.0-alpha.5

http://perf.jenkins.couchbase.com/job/ares/13269/ - 211,815

Test with 3.0.0

http://perf.jenkins.couchbase.com/job/ares/13242/ - 6,655

The regression came in 3.0.0-beta.1

http://perf.jenkins.couchbase.com/job/ares/13271/ - still running will update when finished but its around 6k

These tests are run with 4 kv nodes, 2 replicas and the following commands:

LOAD:

cbc-pillowfight --password password --batch-size 1000 --num-items 20000000 --num-threads 128 --min-size 512 --max-size 512 --persist-to 0 --replicate-to 0 --json --spec "couchbase://172.23.133.13/bucket-1?enable_tracing=false&ipv6=allow" --populate-only

ACCESS:

./cbc-pillowfight --password password --batch-size 1 --num-items 20000000 --num-threads 128 --min-size 512 --max-size 512 --persist-to 0 --replicate-to 1 --json --spec "couchbase://172.23.100.121/bucket-1?ipv6=allow&durability_interval=0.02&enable_tracing=false" --set-pct 100 --num-cycles 500000 --no-population