config.onrendered called too early (before graph is fully rendered)

[garthgoodson]

C3: 0.6.7
D3: 5.7.0
Browser: Chrome 67

This was reported some time ago on the forums, but got no reply. I've updated the fiddle:
http://jsfiddle.net/c80z32pj/

onrendered is called prior to full graph being rendered. In my application the grid is often rendered. I've had to put a settimeout within the onrendered callback which is not ideal...