Retrieve 0 stats/samples when user asked for zero stats/samples

Besides, we also found a bug in influxdb, which will retrieve all stats/samples when user asked for zero stats/samples. The bug could be reproduced with new unit test and it's now fixed.
What about removing this entire function and letting the defaults be 0? We can have the manager apply defaults if it wants and have the UI specify its own. I'm just weary of having defaults in 3 places.