We expect the config server to have oplog entries after the backup checkpoint timestamp here. The operations after the backup are occurring on the shards, and so it's possible the config server doesn't have any new entries. We should perform a no-op on the config server here to ensure that we don't hit this assertion.

One option is to relax the constraint here, but I think the better solution is to perform some no-op on the config server. We could wait the no-op writer (and set the period to 1s) or run an appendOplogNote.