(chart) rackd pod readiness check

- Add a readiness check for the rack pods. This really only applies
  when they are spawned and will not be useful for ongoing readiness
  evaluation. Should eliminate false 'completions' of the chart
  deployment.

Change-Id: I5b547976e770302d2cc293396e1041798ac7e4ea

charts/maas/templates/statefulset-rack.yaml

@@ -76,6 +76,15 @@ spec:
             - /tmp/start.sh
           securityContext:
             privileged: true
+          readinessProbe:
+            initialDelaySeconds: 60
+            periodSeconds: 300
+            timeoutSeconds: 60
+            exec:
+              command:
+                - /bin/bash
+                - -c
+                - journalctl -u register-rack-controller -n 5 | grep -q 'Successfully registered with MaaS Region Controller'
           volumeMounts:
             - mountPath: /sys/fs/cgroup
               name: host-sys-fs-cgroup