Fix a stupid oversight in AggregatedValues
Fix a stupid oversight in AggregatedValues

Both branches of the if are the same, and neither one computes
aggregations! This only works because MarshalJSON calls AggregatedAbsent
before AggregatedValues, and I didn't make the same mistake there.
Cairo, on the other hand, is probably completely broken.

dgryski/carbonapi,errx/carbonapi,nnuss/carbonapi,errx/carbonapi,arodland/carbonapi