data/ml/answer-train.py: Include @70 f2 score in model summary
data/ml/answer-train.py: Go back to cfier_any_picked from prec70 as choice score

This is still after all the number we are interested in.  Fluctuation
improved a lot as we increased size of test set.
data/ml/answer-train.py: Fix too high any_picked score when we have all answers tied.

Happenned with SGDClassifier(loss='modified_huber').