On node dashboard, not work when select special node

[gaopeiliang]

On node info dashboard , it work fine for all node , but when I select one special node , nothing show !!

grafana --- > v5.2

QL: sum((avg(irate(node_cpu_seconds_total{instance=~"$node", mode="system"}[5m])) * 100))

[gaopeiliang]

when I special one node , QL is same as sum((avg(irate(node_cpu_seconds_total{instance=~"$node", mode="system"}[5m])) * 100))

I think is the $node argument is not correct ......

[gaopeiliang]

https://github.com/grafana/kubernetes-app/issues/13