Create a new job if there is an existing job which has failed

Hi!

The delta indexing stop suddenly working for us. We debugged the issue and found a reason:

For debugging and logging purposes, we have configured Delayed Job to keep all failed jobs in `delayed_jobs` table. We found out that if a delta indexing job fails, no new jobs are created. We changed the `where` condition to take into account a situation where we have an existing failed job in `delayed_jobs` table.