fix node_filesystem only collect mountpoint '/' metrics

jsonnet/kube-prometheus/node-exporter/node-exporter.libsonnet

@@ -90,6 +90,7 @@ local k = import 'ksonnet/ksonnet.beta.3/k.libsonnet';
           '--web.listen-address=127.0.0.1:' + $._config.nodeExporter.port,
           '--path.procfs=/host/proc',
           '--path.sysfs=/host/sys',
+          '--path.rootfs=/host/root',
 
           // The following settings have been taken from
           // https://github.com/prometheus/node_exporter/blob/0662673/collector/filesystem_linux.go#L30-L31

manifests/node-exporter-daemonset.yaml

@@ -19,6 +19,7 @@ spec:
         - --web.listen-address=127.0.0.1:9100
         - --path.procfs=/host/proc
         - --path.sysfs=/host/sys
+        - --path.rootfs=/host/root
         - --collector.filesystem.ignored-mount-points=^/(dev|proc|sys|var/lib/docker/.+)($|/)
         - --collector.filesystem.ignored-fs-types=^(autofs|binfmt_misc|cgroup|configfs|debugfs|devpts|devtmpfs|fusectl|hugetlbfs|mqueue|overlay|proc|procfs|pstore|rpc_pipefs|securityfs|sysfs|tracefs)$
         image: quay.io/prometheus/node-exporter:v0.16.0