Update a pool's last work time when the work is popped as well as staged.

cgminer.c

@@ -5062,6 +5062,7 @@ static struct work *hash_pop(void)
 	/* Signal hash_pop again in case there are mutliple hash_pop waiters */
 	pthread_cond_signal(&getq->cond);
 	mutex_unlock(stgd_lock);
+	work->pool->last_work_time = time(NULL);
 
 	return work;
 }