Update singleton job logic to not treat failed jobs as pending instances

If a job completely failed out (will not be retried any further), the logic in `createSingletonJob()` was counting these as still pending. Update the find to treat any job that has errored and not completed as valid to requeue.
Not perfect, but should get the job done. At worst, something gets queued an extra time. We should be writing our jobs so that this isn't super destructive (hopefully).

*Note*
I do not know what updates will need to be applied to the main app's Composer configuration to include these changes.

*Testing*
Please see the comments above the find in `createSingletonJob()` to determine if a new instance should be queued or not.