SelectProcessFailures should ignore previous runs when checking whether the process is finished

https://redmine.teklia.com/issues/8488

1. Run a process with worker activities enabled and at least two tasks, one depending on the other.
2. Stop the first task. The second task stays unscheduled.
3. Retry the process and run it to completion.
4. Try to select all failed worker activities from the worker activity details page.
5. Get an error because the process is not finished.
6. Cry.