nginx ingress header config backwards

[nmnellis]

Nginx ingress controller values are backwards in the nginx template

underscores_in_headers          {{ if $cfg.IgnoreInvalidHeaders }}on{{ else }}off{{ end }};
ignore_invalid_headers          {{ if $cfg.EnableUnderscoresInHeaders }}on{{ else }}off{{ end }};

https://github.com/kubernetes/ingress/blob/master/controllers/nginx/rootfs/etc/nginx/template/nginx.tmpl#L74-L75