Improve the quality of tts_angular, fix train and eval batch sizes (#634)
Summary:
Train (bs=64):

Train bs=64 is default for the model, source: https://github.com/mozilla/TTS/blob/master/TTS/speaker_encoder/config.json#L38
Eval (bs=256):

256 is the largest BS supported by T4.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/634
Reviewed By: aaronenyeshi
Differential Revision: D33026223
Pulled By: xuzhao9
fbshipit-source-id: 623a556792bf40166f6550a3bdd30c1b5c63cb49