Use etcd instead of sqlite for k3s-server

Oh damn, that was so annoying. My cluster ran on near 100% load all the
time! As it turns out that's a known issue on k3s clusters.

The solution is to add the `--cluster-init` flag to the server which let
the server use etcd instead of sqlite. And voila the cpu-usage drops to
a resonably low level in the single digit percent range.

Reference: https://github.com/k3s-io/k3s/issues/10396
Reference: https://docs.k3s.io/datastore/ha-embedded#existing-single-node-clusters

config.yml

@@ -39,6 +39,7 @@ k3s_cluster:
     ansible_user: root
     # note the space between the IPs!
     dns_servers: 8.8.8.8 8.8.4.4
+    extra_server_args: '--cluster-init'
 
 agent:
   vars: