[FEATURE REQUEST] Config to set status code for request rejected because of limit

[ebati]

NGINX Ingress controller version:
quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.10.0

Kubernetes version (use kubectl version):

Server Version: version.Info{Major:"1", Minor:"8", GitVersion:"v1.8.4", GitCommit:"9befc2b8928a9426501d3bf62f72849d5cbcd5a3", GitTreeState:"clean", BuildDate:"2017-11-20T05:17:43Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}

What happened:

Nginx return 503 status code (which is default for nginx) for rate limited request.

What you expected to happen:

I should be able to select status code with limit_req_status directive

Anything else we need to know:

ConfigMap key limit-error-code to set the status code would be great.