Phab/t85378

This PR resolves the issue https://phabricator.wikimedia.org/T85378 . Basically, the Cassandra Node.JS driver caches values so values do not need to be converted always. More info can be found in the task description and commit messages attached to this PR.
I would actually propose to throw an error if the type is anything but a Buffer object (`bytes instanceof Buffer`). Silently handling this might cover up other issues that led to a double conversion.