Fix RoBERTa/XLNet Pad Token in run_multiple_choice.py (#3631)
Fix RoBERTa/XLNet Pad Token in run_multiple_choice.py (#3631)

* Fix RoBERTa/XLNet Pad Token in run_multiple_choice.py

`convert_examples_to_fes atures` sets `pad_token=0` by default, which is correct for BERT but incorrect for RoBERTa (`pad_token=1`) and XLNet (`pad_token=5`). I think the other arguments to `convert_examples_to_features` are correct, but it might be helpful if someone checked who is more familiar with this part of the codebase.

* Simplifying change to match recent commits
huggingface/transformers,huggingface/transformers,huggingface/transformers,huggingface/transformers,huggingface/pytorch-transformers