PUBDEV-3004: Re-enable early stopping when R^2 < 0 (now reported as NaN).
PUBDEV-3004: Re-enable early stopping when R^2 < 0 (now reported as NaN).

h2oai/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,h2oai/h2o-dev,mathemage/h2o-3,mathemage/h2o-3,mathemage/h2o-3,mathemage/h2o-3,jangorecki/h2o-3,mathemage/h2o-3,spennihana/h2o-3,michalkurka/h2o-3,h2oai/h2o-dev,michalkurka/h2o-3,jangorecki/h2o-3,mathemage/h2o-3,h2oai/h2o-dev,h2oai/h2o-dev,h2oai/h2o-3,h2oai/h2o-3,spennihana/h2o-3,spennihana/h2o-3,spennihana/h2o-3,michalkurka/h2o-3,spennihana/h2o-3,h2oai/h2o-dev,jangorecki/h2o-3,spennihana/h2o-3,spennihana/h2o-3,h2oai/h2o-3,jangorecki/h2o-3,jangorecki/h2o-3,michalkurka/h2o-3,h2oai/h2o-dev,h2oai/h2o-3,h2oai/h2o-dev,mathemage/h2o-3,jangorecki/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,jangorecki/h2o-3