copy doc more explicitly in test

jsonobject-couchdbkit does not support .clone() because the functionality seemed super sketchy

(as you can see here: https://github.com/dannyroberts/couchdbkit/compare/master...jsonobject#diff-882a4992bb3ddfef07eb11f5d1178b7bL349, the cloned shares an underlying dict with the original, which seems odd/wrong)


**Note**: tests won't pass because i'm working on fixing another preexisting bug that's causing travis to fail for fluff, but this fixes one particular test failure