eval_failed event: change interface to traceID\tjobsetID

I was not going to break the interface until I noticed the other eval_* events used literal \ts

src/script/hydra-notify

@@ -99,6 +99,7 @@ $listener->subscribe("build_started");
 $listener->subscribe("cached_build_finished");
 $listener->subscribe("cached_build_queued");
 $listener->subscribe("eval_cached");
+$listener->subscribe("eval_failed");
 $listener->subscribe("eval_started");
 $listener->subscribe("hydra_notify_dump_metrics");
 $listener->subscribe("step_finished");