Backporting S3 multi-part upload functionality to glace_store

This commits is to backport S3 multi-part upload functionality
from the old glance store package to glace_store library.

In addition, refactored the write chunk processing to S3 for
a large object and dynamic upload part size calculation to
be able to store large objects via S3 multi-part upload.

Change-Id: Ie01bbf33db5a5ba519c5701ef9475fc0437cd6de
Merge "Backporting S3 multi-part upload functionality to glace_store"