Swift has removed the minimum segment size setting for multipart upload.
To make it compatible with S3, we are re-implementing it in swift3.
Each upload part except the last should be more than the minimum segment
size (default 5MB, same as the S3 multipart upload chunk size). When a
"complete multipart upload" request comes, check all the parts and
return a EntityTooSmall error if they are smaller than the minimum
segment size.
Change-Id: I883b25ab3d43d330ffc60fa2c3ade7a6b5802cee
b348692425