Investigate Perf Regression seen on showfast between build 7.1.0-1250 and 7.1.0-1345

The showfast numbers seemed to have regressed for build 7.1.0-1345.

For e.g, initial build time for test:

1 bucket x 100M x 1KB, 100K KV ops/sec, single 2i index, no mutations during initial build only

 is 5.8 min (1345 build) vs 2.9 min in (1250 build)

http://showfast.sc.couchbase.com/#/runs/secondary_100M_plasma_initial_nyx/7.1.0-1345

http://showfast.sc.couchbase.com/#/runs/secondary_100M_plasma_initial_nyx/7.1.0-1250