Incorrect position in icon-position example

[gberaudo]

The left icon should have its text anchored to the bottom.
This is not the case:

This is due to OL returning a null anchor: iconStyle.getAnchor() during first rendering.

If you click "toggle clampToGround", the text will be placed correctly.

I think that as soon as the icon is actually loaded by OpenLayers, then subsequent calls to iconStyle.getAnchor() will return a valid anchor.

In order to fix this issue, we should thus track the loading state of the image and (re)create the counterpart geometry when it changes.