Fix passing through the indicator span timer field name
Fix passing through the indicator span timer field name

This got set too late - since the metric extraction sink gets
initialized way ahead of us initializing the field it depends
on (which is a one-off field anyway), let's just drop the field and
make the sink directly from config.

evanj/veneur,evanj/veneur,stripe/veneur,stripe/veneur,gphat/veneur,gphat/veneur,gphat/veneur,evanj/veneur