collectd: Add DaemonSet for collectd

Since all the nodes in the cluster run Fedora CoreOS now, we can
deploy collectd as a container, managed by a DaemonSet.

Note that while _collectd_ has to run as _root_ in order to collect
a lot of metrics, it should not run with all privileges.  It does need
to run as a "super-privileged container" (`spc_t` SELinux domain), but
it does _not_ need most kernel capabilities.

collectd/kustomization.yaml

@@ -0,0 +1,34 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+namespace: collectd
+
+labels:
+- pairs:
+    app.kubernetes.io/instance: collectd
+    app.kubernetes.io/part-of: collectd
+  includeSelectors: false
+
+resources:
+- namespace.yaml
+- collectd.yaml
+
+configMapGenerator:
+- name: collectd
+  files:
+  - collectd.d/df.conf
+  - collectd.d/log.conf
+  - collectd.d/plugins.conf
+  - collectd.d/prometheus.conf
+
+patches:
+- patch: |-
+    apiVersion: apps/v1
+    kind: DaemonSet
+    metadata:
+      name: collectd
+    spec:
+      template:
+        spec:
+          nodeSelector:
+            du5t1n.me/collectd: 'true'