[maps] vector tile load errors not displayed in legend

[nreese]

Steps to view problem

1. Running locally, Install sample web logs
2. install trial license
3. create map
4. add clusters layer
5. select 'hexagons'
6. save map
7. revert to trial license
8. open map.

Notice how not data is loaded and legend shows empty icon instead of error

Opening the browser web tools, there are 2 problems.
1)The tiles are returned with 200 status code. The kibana vector tile routes need to be updated to pass elasticsearch status code to the client.
2) The client needs to update layer error state when error event is fired.

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)