High CPU within the `process.title`

Consider the following code:
```js
for (var i=0; i <= 256; i++) {
  worker = conn.worker('name', factory);
  worker.start();
}
```
When there is no data for this worker, these workers still invoke `poll` repeatedly, that means in one time, a process's title would be changed 256 times in this case, that might cause a high cpu process and an increasing memory usage. You can run this simple code for test in your machine, so I think sleep over these `procline` will be a good solution for this bug or hidden danger.