Features flash when transitioning between expression + constant values

Nobody has claimed this yet.

**mapbox-gl-js version**: 0.44.2

**browser**: Chrome 65.0.3325.181

### Steps to Trigger Behavior

1. Create a layer styled with a constant property.
2. Change property to expression-based property (not sure if all expressions, but at least with a `match` expression)
3. Styled properties flicker when switching between constant and expression-based properties.

### Link to Demonstration

* https://jsfiddle.net/lbud/ar1c8trq/1/ : fill layer; mouseover/off features for disappearing flash (disappearing also happens for other layer types including [line](https://jsfiddle.net/lbud/vdc1rmu6/1/))
* https://jsfiddle.net/lbud/jfewqzdz/1/ : fill-extrusion layer; mouseover/off features for flash of black

### Expected Behavior

Previously calculated paint values remain rendered until the first frame when recalculated values are ready, so there is no intermediary flash of any other value besides the two specified

### Actual Behavior

Flash of either transparent or black

cc @anandthakker @kalimar

Reproduce the transition using the linked JSFiddle examples, including fill, line, and fill-extrusion layers, and compare constant-to-expression changes. Trace the rendering path for paint-property updates; done means previously calculated values remain visible until recalculated values are ready, without a transparent or black intermediary flash.

Written by the indexing model from the issue text.