Important fix for cpu usage in adet/modeling/attn_predictor.py

[doanthuyennt]

Hello again Mr author, There is a bug I came a cross when I use only cpu for predicting, What my approach was to change every to.("cuda") in to to(rois.device) ## Since I want to be consistent with your code anyway. After that, run python setup.py install -v again ... and voila it worked!

Tks for reading this.