Add pcg to ignore impl/prod
Add pcg to ignore impl/prod

This should fix the travis redness.

TBR=dnj@chromium.org, estaab@chromium.org, maruel@chromium.org, tandrii@chromium.org, vadimsh@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1334833002 .

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go