HTTP2 broken in webhook server in v0.2.0-alpha.0

[lmunro-at-shopify]

The rework of the certificate generation seems to have removed support for HTTP2 as a side effect.

We now call http.Server.Serve instead of the old ListenAndServeTLS:

controller-runtime/pkg/webhook/server.go

Line 166 in 856708d

err = srv.Serve(listener)

Serve does not default to http2. It must be configured manually in the listener:

// HTTP/2 support is only enabled if the Listener returns *tls.Conn
// connections and they were configured with "h2" in the TLS
// Config.NextProtos.
//

It should be a small thing to fix.
I am going to submit a PR if can just get though signing the CLA, unless someone tells me this works as designed, in which case it should probably be mentioned somewhere in the release notes.