Use GOVUK_STATSD_PREFIX when available
Use GOVUK_STATSD_PREFIX when available

This helps us balance statsd requests across distributed hosts.

See alphagov/puppet@5bec09fd02820 for more information.

ggoral/whitehall,askl56/whitehall,robinwhittleton/whitehall,askl56/whitehall,robinwhittleton/whitehall,hotvulcan/whitehall,YOTOV-LIMITED/whitehall,alphagov/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,YOTOV-LIMITED/whitehall,YOTOV-LIMITED/whitehall,hotvulcan/whitehall,robinwhittleton/whitehall,ggoral/whitehall,alphagov/whitehall,askl56/whitehall,hotvulcan/whitehall,alphagov/whitehall,robinwhittleton/whitehall,ggoral/whitehall,askl56/whitehall,alphagov/whitehall,hotvulcan/whitehall