k3s systemd service should wait until the server is ready

[erikwilson]

If the k3s service is started and we immediately attempt to use the service it may fail:

root@eeabbe84a77e:~# systemctl stop k3s.service && systemctl start k3s.service && k3s kubectl get nodes
The connection to the server localhost:6443 was refused - did you specify the right host or port?
root@eeabbe84a77e:~# systemctl stop k3s.service && systemctl start k3s.service && k3s kubectl get nodes
Unable to connect to the server: x509: certificate signed by unknown authority (possibly because of "crypto/rsa: verification error" while trying to verify candidate authority certificate "k3s-ca")