Creating draft submission results in new entity

[matthew-white]

@lognaturel and I discussed this issue here. A draft submission (a submission created while testing a form draft) shouldn't result in a new entity. That wasn't possible previously because draft submissions can't be approved. However, now that entities can be created on submission receipt, it's a possibility. You can see that in this project: https://staging.getodk.cloud/#/projects/28. I published the form "Tree registration", creating a dataset. I then uploaded a second form, "Tree registration 2", which creates entities in the same dataset. I didn't publish it, but I created a draft submission. Doing so created an entity in the dataset.

This behavior seems to be true of all draft submissions, whether for a draft form that has never been published or for a draft of a form with a published version.