Move kubelet runtime.cgroups into image metadata

Since they are passed to kubelet from kublet.sh inside the image this seems a
better place.

Signed-off-by: Ian Campbell <ijc@docker.com>

Author: Ian Campbell

pkg/kubelet/build.yml

@@ -26,6 +26,9 @@ config:
   rootfsPropagation: shared
   pid: host
   runtime:
+    cgroups:
+    - systemreserved
+    - podruntime
     mkdir:
     - /var/lib/kubeadm
     - /var/lib/cni/conf

yml/kube.yml

@@ -42,10 +42,6 @@ services:
   - name: kubelet
     image: linuxkit/kubelet:0e6902fbb878f592b8be03605e18d917e622ce31
     cgroupsPath: podruntime/kubelet
-    runtime:
-      cgroups:
-        - systemreserved
-        - podruntime
 files:
   - path: etc/linuxkit.yml
     metadata: yaml