add for rkt as well

roles/kubernetes/node/templates/kubelet.rkt.service.j2

@@ -20,6 +20,7 @@ ExecStartPre=-/bin/mkdir -p /var/lib/kubelet
 EnvironmentFile={{kube_config_dir}}/kubelet.env
 # stage1-fly mounts /proc /sys /dev so no need to duplicate the mounts
 ExecStart=/usr/bin/rkt run \
+        --volume os-release,kind=host,source=/etc/os-release \
         --volume dns,kind=host,source=/etc/resolv.conf \
         --volume etc-kubernetes,kind=host,source={{ kube_config_dir }},readOnly=false \
         --volume etc-ssl-certs,kind=host,source=/etc/ssl/certs,readOnly=true \
@@ -39,6 +40,7 @@ ExecStart=/usr/bin/rkt run \
         --mount volume=opt-cni,target=/opt/cni \
         --mount volume=var-lib-cni,target=/var/lib/cni \
 {% endif %}
+        --mount volume=os-release,target=/etc/os-release \
         --mount volume=dns,target=/etc/resolv.conf \
         --mount volume=etc-kubernetes,target={{ kube_config_dir }} \
         --mount volume=etc-ssl-certs,target=/etc/ssl/certs \