SubsurfaceViewer: Rendering loop when using multiple views with the same layer

[Anders2303]

Noticed that the the wells layer keeps re-rendering when you have multiple viewports that share the layer.

As an example, add a log in the WellsLayer.renderLayers() method, and go to a story that shows the layer in two views (such as this label position example) and you'll see the log repeating.

[Anders2303]

Oh, it also seems to be a slight difference between defining the view-type via viewType and use3d. If using viewType, the loop happens immediately, but if you do it with use3d the loop doesn't happen until you begin moving the camera...