Fix signature mismatches during sandbox upload

This reverts commit cf984bf, which introduced the bug in RiotGames/berkshelf#409.

I spent some time trying to rectify the situation, but as @eklein mentioned in the issue, it is impossible to reproduce once a cookbook uploads successfully.

I think we should revert these changes, and not reintroduce them until the changes have been tested with a new cookbook being uploaded to a chef server.

/cc @hannesg @reset any ideas?