Prepending bucket name for virtual path requests

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Note

We are still interested in understanding the impact of this change, but have decided to temporarily introduce the S3_STYLE configuration option virtual-v2 that enables the below-described functionality. Please use this option to test your compatibility and let us know here if it works for you. The default behaviour will remain unchanged.

Hi All, we are about to ship a feature to support the S3 Express One Zone buckets and I was able to simplify how the s3 hostname for is calculated for S3_STYLE=virtual configurations (which is the default). This normalizes:

• The actual request to S3
• The Host header
• The host element of the V4 signature canonical headers

The primary change is that we are moving from this:

server ${S3_SERVER}:${S3_SERVER_PORT};

to this:

server ${S3_BUCKET_NAME}.${S3_SERVER}:${S3_SERVER_PORT};

when forwarding the request to S3. .According to the latest documentation, this is the preferred way of making requests for "virtual" path style endpoints which every bucket in S3 should support. https://docs.aws.amazon.com/AmazonS3/latest/userguide/VirtualHosting.html

Here is the pull request. I will wait for a few days to see if are any concerns here before merging.
#229

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I have confirmed that this change is compatible with DigitalOcean's Object Spaces