updating legacy op throttling to be more stable
updating legacy op throttling to be more stable

Change-Id: I8cd85621918c49b197b0438f3cafe06b3c3d94b8
Reviewed-on: http://review.couchbase.org/c/perfrunner/+/132385
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Bo-Chun Wang <bb86fd206c9c35341feb9b50e74a74a83e254d63@couchbase.com>

couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner