public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
        Runnable work = associateWithSubject(command);
        return this.targetScheduledExecutorService.scheduleAtFixedRate(work, initialDelay, period, unit);
    }
Same concept as the {@link SubjectAwareExecutorService} but additionally supports the
{@link ScheduledExecutorService} interface.
core/src/main/java/org/apache/shiro/concurrent/SubjectAwareScheduledExecutorService.java