cilium: mount the host's /etc/hosts on gossip clusters - #18465

On gossip clusters, protokube updates the host's /etc/hosts as
control-plane nodes are replaced, but kubelet only copies that file
into host-network pods at container start. The cilium agent and
operator are pointed at api.internal.<cluster> via
KUBERNETES_SERVICE_HOST, so after a control-plane rolling update they
keep dialing the old addresses until the pods are recreated.

Mount /etc/hosts from the host (as kube-proxy already does on gossip
clusters) so the agent and operator observe protokube's updates and
reconnect on their own.