This config will enable Nginx to listen on port 80, and act as a reverse proxy for grafana (refer to the custom ini root_url section below), and Influx DB. 
Influx DB has a problem where it is using root path on admin UII (refer [issue#5352](https://github.com/influxdata/influxdb/issues/5352)) and this config handles it via referrer and api end point redirects.