m/n/kubernetes: serve authproxy with node certificate

We are currently serving authproxy with the Kubernetes node certificate,
which is somewhat useless, considering that this certificate isn't even
issued by the same CA that the client certificates (which are Metropolis
certificates) presented.

This changes the authproxy to serve with Metropolis node certificates
instead.

Change-Id: I03ff19c919c6a9fa72c98997432cc06a59e9958e
Reviewed-on: https://review.monogon.dev/c/monogon/+/2740
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/node/kubernetes/service_controller.go b/metropolis/node/kubernetes/service_controller.go
index fbeabca..804a210 100644
--- a/metropolis/node/kubernetes/service_controller.go
+++ b/metropolis/node/kubernetes/service_controller.go
@@ -48,7 +48,7 @@
 	KPKI    *pki.PKI
 	Root    *localstorage.Root
 	Network *network.Service
-	Node    *identity.Node
+	Node    *identity.NodeCredentials
 }
 
 type Controller struct {