Allow config to disable geoip

[bputt]

Is this a BUG REPORT or FEATURE REQUEST? (choose one): Feature
NGINX Ingress controller version: 0.11.0
Kubernetes version (use kubectl version): 1.9.2

In an offline environment, it'd be great to disable the geoip feature.

In the nginx.tmpl, it'd be great if you'd add something like the following:

{{ if $cfg.UseGeoIPTagging }}
geoip_country       /etc/nginx/geoip/GeoIP.dat;
geoip_city          /etc/nginx/geoip/GeoLiteCity.dat;
geoip_org           /etc/nginx/geoip/GeoIPASNum.dat;
geoip_proxy_recursive on;
{{ end }}

For backwards compatibility, UseGeoIPTagging could default to true