Mapbox plugin for QtLocation no longer uses cache when offline

The older mapbox plugin starting at 5.9.2 will no longer use the tile cache when offline. It will just complain it can't connect to the mapbox url.

To replicate:
-Use the attached places_map.qml in place of the file with the same name in the Locations "places_map" example. Add your own access token to the plugin parameter.
-Compile and run "places_map" example using at least Qt 5.9.2 while online. Tiles should appear in the view. Exit "places_map".
-Go offline and reopen "places_map" example. Tiles will fail to appear from the cache.