[tensorflow_rcnn] distributed_tensorflow_mask_rcnn/mask-rcnn-fsx.ipynb issues

https://github.com/awslabs/amazon-sagemaker-examples/blob/master/advanced_functionality/distributed_tensorflow_mask_rcnn/mask-rcnn-fsx.ipynb

This notebook doesn't use default buckets and requires to much boiler plate to be filled by a customer making it cumbersome.

Open advanced_functionality/distributed_tensorflow_mask_rcnn/mask-rcnn-fsx.ipynb and review how bucket settings and customer-provided values are handled. Compare the notebook's current setup with the request to use default buckets and reduce boilerplate; done means the example requires less customer configuration while still running successfully.

Written by the indexing model from the issue text.