Remove verbose log message from tumble
Remove verbose log message from tumble

R=nodir@chromium.org, vadimsh@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2228793002

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