Support using local S3 instance (e.g. minio)

[larsll]

Is your feature request related to a problem? Please describe.
We are working on setting up local/offline DeepRacer training; using Sagemaker and Robomaker. This means having a local S3 instance (using minio) to host the files.

Describe the solution you'd like
It should be possible to configure the S3 Endpoint URL to point to a specific local URL/port. Current proposal is to allow to pass a pre-configured s3Client into an Estimator on creation.

Describe alternatives you've considered
An alternative would be to store the required configuration in the Sagemaker Local Session. It would nevertheless require changes to all areas of code where a new s3Client is created.

[laurenyu]

Thanks again for submitting #1359! Did it address your issue (or is there more you're looking for with this)?

[larsll]

Yes - this can be closed. #1359 solved this issue -- we no longer need a fork to support local S3 instances (e.g. minio).