component.Base: isVdomUpdating change does not honor render

Hi Nige,

I am wondering about this change:

We also set this flag to true when calling render(). This is important, since updates which arrive while the initial rendering cycle is running need to get delayed.

If you want to keep:

    get isVdomUpdating() {
        // The VDOM is being updated if we have the promise that executeVdomUpdate uses
        return Boolean(this.vdomUpdate)
    }

we need to adjust all setters to modify this.vdomUpdate to a promise or null instead.