src/core/sched_ctx.c: fix #13209, we are looping on the masters, not the workers

src/core/sched_ctx.c

@@ -1071,7 +1071,7 @@ int _starpu_nworkers_able_to_execute_task(struct starpu_task *task, struct _star
 
 	while(workers->has_next_master(workers, &it))
 	{
-		worker = workers->get_next(workers, &it);
+		worker = workers->get_next_master(workers, &it);
 		STARPU_ASSERT_MSG(worker < STARPU_NMAXWORKERS, "worker id %d", worker);
 		if (starpu_worker_can_execute_task(worker, task, 0))
 			nworkers++;