Improve perf of `_user_gen` by using `itertools.cycle`
Improve perf of `_user_gen` by using `itertools.cycle`


mbeacom/locust,mbeacom/locust,mbeacom/locust,locustio/locust,mbeacom/locust,locustio/locust,locustio/locust,locustio/locust