engines/http: Add storage class option for s3

engines/http: Add storage class option for s3

Amazon S3 offers a range of storage classes that you can choose from
based on the data access, resiliency, and cost requirements of your
workloads. (https://aws.amazon.com/s3/storage-classes/)

For example, we have **STANDARD** storage class to test normal
workload, and have **COLD** storage class to test the workload
with gzip compression. It is convenient to select which
storage class to access for different kinds data.

Signed-off-by: Feng, Hualong <hualong.feng@intel.com>