Disable gzip auto decoding

### Which service(blob, file, queue) does this issue concern?

blob

### Which version of the SDK was used? Please provide the output of `pip freeze`.

Azure 4.0.0, blob 1.4.0

### What problem was encountered?

When downloading a gzipped file that contains `Content-Encoding: gzip` through `get_blob_to_stream`, the file is automatically decoded. This was reported at #509. However, I find the workaround not to be maintainable since it messes with private method/classes. I believe this is a valid use-case, one may want a file to be decoded by the browser but not when fetching it through the API.

### Have you found a mitigation/solution?

No

Note: for table service, please post the issue here instead: https://github.com/Azure/azure-cosmosdb-python.