Fix exception handling in POST /submission

[jcadam14]

Because this exception handling could happen after storing the submission object in the database, there is a possibility of a submission being in the SUBMISSION_STARTED or SUBMISSION_UPLOAD state. Easiest thing is to set the UPLOAD_FAILED state, but it's possible this won't do anything if the issue is in database updates. But best to at least try. Another option would be to remove a created SUBMISSION if an exception hits here so that a submission isn't stuck in some state, but again if the issue is with updating a database, not much chance of that working.