A new home for 404-server (defaultbackend)

[jonpulsifer]

👋 we recently bumped the defaultbackend to version 1.5 in kubernetes/ingress-nginx#3125 to conceal /metrics/ behind port 10254

During that discussion a PR was merged to not require the defaultbackend service for ingress-nginx.

I originally moved the 404-server into the old kubernetes/ingress repo from contrib, but now we've gone our separate ways w/ nginx and gce so I'd like to find a new home for this image.

Should we move it here? I think so? Is there a better place? I don't think it makes sense for the ingress-nginx repo to own this image any longer.

[bowei]

Yes -- also, we should probably use something even simpler and smaller (thttpd?).

[rramkumar1]

/kind cleanup