Fix show jobs list when room name undefined.

Hello. 

In latest hubot-cron, room name is undefined when show `list jobs`.
cause, new define job is `reply_to` and `room` attributes has `jobs[1].user`.
I've made the modifications corresponding to both of the new definition and the old definition Job.

before
```
795789: 30 18 * * 1-5 @room_name "Hello." // Before hubot-cron update defined job.
862341: 58 9 * * * @undefined "test" // After hubot-cron update defined job.
```

after
```
795656: 30 18 * * 1-5 @room_name "Hello."
867501: 58 9 * * * @room_name "test"
```

Please confirm.
Thank you.