write a test ensuring the index-scheduler is effectively down when the upgrade task fail and try to process it when it restarts. There is a bug when deleting this task

crates/index-scheduler/src/scheduler/process_batch.rs

@@ -329,6 +329,8 @@ impl IndexScheduler {
 
                 for task in tasks.iter_mut() {
                     task.status = Status::Succeeded;
+                    // Since this task can be retried we must reset its error status
+                    task.error = None;
                 }
 
                 Ok(tasks)