Feature Request: Allow Support for Upstream Keep-Alive Timeout

[diazjf]

Currently there does not seem a way to change the keepalive_timeout[1] for the Upstream. It is only available in the http block which applies to http, server, location.

They need to be added via ConfigMap changes to the template[2]. If there is another way of configuring this it should be documented.

[1]http://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive_timeout
[2] https://github.com/kubernetes/ingress-nginx/blob/master/rootfs/etc/nginx/template/nginx.tmpl#L410-L420

[diazjf]

I see it is a duplicate of #3099. Will closw :)