true/false: defined as boolean values in a task yaml, but defined as strings in pipeline config

Hi,

We've noticed a problem when a task config defines a boolean param, without quotes:

```
params:
    MY_PARAM: false
```

The problem is that evaluating `$MY_PARAM` in the task script gets rendered as a `0` rather than as `false`. On the other hand, if you try to override the value in the pipeline config, the value gets rendered instead as a string: `"false"`.

Thanks,

Al && @dsabeti
