Fix for wrapper function returning 0ms timings

DEBUG: Bad line: 0,ms in msg "production.timer:0|ms"
https://github.com/etsy/statsd/blob/5b900711191a9c5cfd536c877a3c119d1df5679a/lib/helpers.js#L35
return isNumber(fields[0]) && Number(fields[0]) > 0;

statsD expects a > 0 number for ms counters.