update events don't pass event info

I'm pretty sure that `evt` is always undefined at this line for update-start/update-end events:

https://github.com/Esri/cedar/blob/2a357d05489fd0162dd350ce556a680e4c93f0f4/src/cedar.js#L788

In this case I think we ought to provide an object like:
```
{
type: evtName
}
```