kubernetes: Manage worker nodes

So far, I have been managing Kubernetes worker nodes with Fedora CoreOS
Ignition, but I have decided to move everything back to Fedora and
Ansible.  I like the idea of an immutable operating system, but the FCOS
implementation is not really what I want.  I like the automated updates,
but that can be accomplished with _dnf-automatic_.  I do _not_ like
giving up control of when to upgrade to the next Fedora release.
Mostly, I never did come up with a good way to manage application-level
configuration on FCOS machines.  None of my experiments (Cue+tmpl,
KCL+etcd+Luci) were successful, which mostly resulted in my manually
managing configuration on nodes individually.  Managing OS-level
configuration is also rather cumbersome, since it requires redeploying
the machine entirely.  Altogether, I just don't think FCOS fits with my
model of managing systems.

This commit introduces a new playbook, `kubernetes.yml`, and a handful of
new roles to manage Kubernetes worker nodes running Fedora Linux.  It
also adds two new deploy scripts, `k8s-worker.sh` and `k8s-longhorn.sh`,
which fully automate the process of bringing up worker nodes.

hosts

@@ -11,6 +11,9 @@ bw0.pyrocufflink.blue
 [btop]
 chromie.pyrocufflink.blue
 
+[btop:children]
+kubelet
+
 [burp-client]
 bw0.pyrocufflink.blue
 cloud0.pyrocufflink.blue
@@ -24,6 +27,7 @@ git0.pyrocufflink.blue
 [collectd]
 
 [collectd:children]
+kubelet
 pyrocufflink
 
 [collectd-prometheus:children]
@@ -84,8 +88,13 @@ burp-server
 [k8s-controller]
 k8s-ctrl0.pyrocufflink.blue
 
+[k8s-longhorn]
+
 [k8s-node]
 
+[k8s-node:children]
+k8s-longhorn
+
 [kubelet:children]
 k8s-controller
 k8s-node
@@ -105,6 +114,9 @@ minio-backups
 [nfs-client:children]
 k8s-node
 
+[no-firewalld:children]
+kubelet
+
 [needproxy]
 nvr2.pyrocufflink.blue