Add BucketLocation detection

Previously it was possible with the Minio S3 SDK to set ServerAddress and omit BucketLocation. It seems that Minio would perform a GetBucketLocation API call: https://github.com/minio/minio-go/blob/589ff8dc7dd161d4e0ebeb96c2988f055fcec713/bucket-cache.go#L83-L117

To preserve backwards compatibility, we may want to add this to the AWS v2 adapter.