cmd/k8s-operator: restart ProxyGroup pods less (#14045)

We currently annotate pods with a hash of the tailscaled config so that
we can trigger pod restarts whenever it changes. However, the hash
updates more frequently than is necessary causing more restarts than is
necessary. This commit removes two causes; scaling up/down and removing
the auth key after pods have initially authed to control. However, note
that pods will still restart on scale-up/down because of the updated set
of volumes mounted into each pod. Hopefully we can fix that in a planned
follow-up PR.

Updates #13406

Signed-off-by: Tom Proctor <tomhjp@users.noreply.github.com>

cmd/k8s-operator/proxygroup_specs.go

@@ -93,6 +93,10 @@ func pgStatefulSet(pg *tsapi.ProxyGroup, namespace, image, tsFirewallMode, cfgHa
 	c.Image = image
 	c.VolumeMounts = func() []corev1.VolumeMount {
 		var mounts []corev1.VolumeMount
+
+		// TODO(tomhjp): Read config directly from the secret instead. The
+		// mounts change on scaling up/down which causes unnecessary restarts
+		// for pods that haven't meaningfully changed.
 		for i := range pgReplicas(pg) {
 			mounts = append(mounts, corev1.VolumeMount{
 				Name:      fmt.Sprintf("tailscaledconfig-%d", i),