fix typo in variable ProxyRealIPCIDR

[gianrubio]

I was running the default template for the ingress controller. I realised a typo in configuration, only renaming the var solve the issue.

Args

# ./nginx-ingress-controller 
--default-backend-service=kube-system/default-http-backend 
--tcp-services-configmap=kube-system/tcp-configmap 
--configmap=kube-system/nginx-load-balancer-conf

Error

...
W1212 13:18:13.925417      19 controller.go:833] service */* does not have any active endpoints
W1212 13:18:14.006342      19 queue.go:82] requeuing gitlab/kubedash, err template: nginx.tmpl:17:31: executing "nginx.tmpl" at <$cfg.ProxyRealIpCidr>: can't evaluate field **ProxyRealIpCidr** 
in type config.Configuration

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[k8s-reviewable]

This change is 

[gianrubio]

I signed it

[coveralls]

Coverage remained the same at 39.753% when pulling bd9ec42 on gianrubio:typo-realipcidr into 697cf2d on kubernetes:master.

[aledbf]

LGTM

[aledbf]

@gianrubio thanks!