Fixed an error related to the task indicator of the tagger during inference.
Changes:

- Fixed a bug where the task indicator for each tagging instance is always set to be TN _during inference_. This bug only affects the evaluation of ITN scores. I re-evaluated all the models. All the ITN scores changed only a tiny bit. For German duplex model though, the ITN score went from 79.89% to 87.15% after the bug is fixed.
- Removed data augmentation for the tagger. After the bug is fixed, I tried several times and found data augmentation for the tagger does not improve the performance. data augmentation for the decoder still improves performance.

@yzhang123 