When completing a multipart-upload, include the upload-id in sysmeta.
If we can't find the upload marker, check the final object name; if it
has an upload-id in sysmeta and it matches the upload-id that we're
trying to complete, allow the complete to continue.
Also add an early return if the already-completed upload's ETag matches
the computed ETag for the user's request. This should help clients that
can't take advantage of how we dribble out whitespace to try to keep the
conneciton alive: The client times out, retries, and if the upload
actually completed, it gets a fast 200 response.
Change-Id: I38958839be5b250c9d268ec7c50a56cdb56c2fa2
02548717ac