Permit perf test duration to be set, seconds, by environment variable…#660

StuartWheater merged 2 commits intodatashield:v6.3.6-devdatashield/dsBaseClient:v6.3.6-devfrom

StuartWheater:v6.3.6-dev_feat-perf-supportStuartWheater/dsBaseClient:v6.3.6-dev_feat-perf-supportCopy head branch name to clipboard