Revert mapConfigToMMLBuilderConfig to work synchronously
Revert mapConfigToMMLBuilderConfig to work synchronously

The overviews metadata is now collected elsewhere (Windshaft-cartodb)
and passed in the MapConfig, so no asynchronous processing is needed
to support verctor overviews.

CartoDB/Windshaft,CartoDB/Windshaft,CartoDB/Windshaft