OpenStreetMap No Consistent Language

## Expected Behavior

I would expect the country names in the visualization to default to the graylog server language.

## Current Behavior

The country names in the visualization default to the regions local language. ie. All of the middle eastern countries are shown in Arabic, rather than their names per the graylog server language.


## Possible Solution

Configure openstreetmap to use the localization of the graylog server.

## Steps to Reproduce (for bugs)

1. Configure graylog server for English.
2. Configure geo-location plugin.
3. Render world map visualization.
3. Look at Middle Eastern countries.
4. Shown on map with arabic names, instead of english versions.

## Context

Trying to make use of the world map to show log sources geo location. Not multi-lingual.

## Your Environment

* Graylog Version: graylog-server-2.5.1-1.noarch
* Elasticsearch Version: elasticsearch-6.5.4-1.noarch
* MongoDB Version: mongodb-org-server-2.6.12-1.x86_64
* Operating System: Centos-7
* Browser version: Chrome 71.0.3578.98 (Official Build) (64-bit)