Currently, since we pin the stable timestamp behind the prepare timestamp, we do not have rollback test coverage for transactions that were prepared before the stable timestamp. 

We would only allow it to move forward after its commit/abort oplog entry has been majority committed, which means that it would not be in the prepared state during a rollback.

Once we stop pinning the stable timestamp, we should test that transactions prepared before the stable timestamp end up in the prepared state after a rollback.