The same file is uploaded to two nodes results in only one file in /private

Issue Summary

I believe the Upload module's standard behavior is to rename incoming files if they conflict with an existing file. It appears the Private Upload module does not check for duplicates. I don't know if this results in the first file being overwritten or the second file being disregarded. However, deleting either of the two nodes will result in the file being removed, which makes it inaccessible to the second node.