FRCNN in the LXMERT demo outputs different features when using a local image vs. an image from a URL 
## Environment info
- `transformers` version: 3.3.1
- Platform: Linux-5.4.0-52-generic-x86_64-with-debian-buster-sid
- Python version: 3.7.4
- PyTorch version (GPU?): 1.6.0 (False)
- Tensorflow version (GPU?): not installed (NA)
- Using GPU in script?: No
- Using distributed or parallel set-up in script?: No

### Who can help
@eltoto1219

## Information
Model I am using: LXMERT, more specifically FRCNN. The problem arises when using the demo.ipynb file given here: https://github.com/huggingface/transformers/blob/master/examples/lxmert/demo.ipynb

## To reproduce

1. Change the URL to the filename of a local image. Both the visualization and the extracted features are affected by this.

## Expected behavior
I noticed that the order of Red, Green, Blue is changed in this line in the utils file: https://github.com/huggingface/transformers/blob/7abc1d96d114873d9c3c2f1bc81343fb1407cec4/examples/lxmert/utils.py#L552

When I comment out this line, the visualization and the features output by the model for a local image are the same as when we use its URL without commenting this line out. 

I would appreciate if you can confirm that commenting out that line does not cause other issues in LXMERT so that I can use local files.

Best,
Ece  

Pinging @eltoto1219 <|||||>Hi @eltoto1219 I see that my issue and proposed solution have been mentioned in a more recent issue (#8769), should I follow there for the confirmation?<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.