Data points do not display if JSON endpoint takes longer to respond than the query

[amotl]

@stevemandl reported over at grafana#220 (comment) the other day:

If the json endpoint takes longer to respond than the query, there are no map points rendered. I was able to get it to work when the query I was using took a long time to respond (longer than the JSON location response), but when I optimized my query to run faster this behavior started. The workaround I am using is to hit the refresh button after the locations have had a chance to load.

He already verified that behavior with our fork and confirmed that it does not fix this issue yet even if the updated code base uses .refresh() rather than .render() through https://github.com/panodata/grafana-map-panel/blob/0.9.0/src/worldmap_ctrl.ts#L233-L240, as outlined within grafana#221.

cc @xiaobeiyang