Test Cloudfront Cache Policy for Neuroglancer

[aaronkanzer]

Relates to #160

A new cache policy was implemented in CloudFront for both staging and production distributions.

The purpose of this Issue is to ensure that the cache does clear immediately (e.g. in 1 second with regards to TTL on the cache polcy)

The suggested test is to 1. upload a zarr, 2. view zarr successfully in neuroglancer, 3. overwrite a file in S3 for the given zarr that would render differently in neuroglancer, 4. observe difference in neuroglancer immediately

Cc @kabilar