Don't create drafts every time a component is edited.

TNL-399
I agree with @dmitchell that I don't see a use case for an xblock needing to persist a change caused simply by rendering the xblock's Studio view. Any change that the xblock needs to do when it is rendered can easily be done the next time, and it seems odd that merely bringing up the Studio editor would have a side effect (Would the xblock's state change based on the number of times a course member opens the editor? Editing and then pressing Cancel seems like something that should have no impact on the state of the xblock).

Therefore I am leaning towards removing the call to update_item above. However, I am also worried about the difference in behavior between split mongo and old draft mongo in the case of editing an xblock and pressing Save with no changes. In split, this will not create a draft, but it will in old mongo. The difference in behavior could be confusing, as both modulestores will be in use simultaneously.

I've asked @explorerleslie to weigh in on this, and also sent @cpennington a message in Hipchat. I'm starting to think that the best thing to do would be to make old draft mongo and split behave consistently.