if all iterations are completed, I don't want to wait until the train-time reaches 0

### System information

- **Windows 10.0.19041**:
- **.NET Core 3.1.402**:

### Issue
- **What did you do?**
With each command I need to specificy the train time. e.g.
`mlnet regression --dataset "Step2.csv" --label-col "Position" --has-header true --train-time 3600 --cache on`
- **What happened?**
I noticed that there are max 70 iterations. If all the iterations are completed before the train-time ends, I have to wait untill it counts till 0 before it outputs the best iteration & generates the example code.
- **What did you expect?**
If the max amount of iterations have been completed, the training should stop. There is no need to wait until the countdown goes to 0 while being idle.