[Bug] ListObjects returns multi-part upload part files

[TimJRodgers]

Using the .Net client, with an empty Fake S3 bucket, I perform a multipart upload;

InitiateMultipartUpload()
UploadPart()
UploadPart()
UploadPart()
CompleteMultipartUpload()

Then I call ListObjects(). I get not only the completed object, but all the parts as well. So, 4 objects in S3Objects for the response of ListObjects().