Improve deterministic ImageNet baseline

[dustinvtran]

I'm thinking of efficientnet or assemble-resnet. Both have TF implementations:

• https://github.com/clovaai/assembled-cnn
• https://github.com/tensorflow/tpu/tree/master/models/official/efficientnet/tpu (which I believe is still in the process of converting to Keras/TF 2.0)

[dustinvtran]

Moved to https://github.com/google/uncertainty-baselines/issues/61.