fix: kubelet rules group_left

When the right hand-side of the operations returns multiple
matches the rules fails. This fix aim to prevent such failure.

Author: Davide Bizzarri

rules/kubelet.libsonnet

@@ -11,7 +11,12 @@
           {
             record: 'node_quantile:kubelet_pleg_relist_duration_seconds:histogram_quantile',
             expr: |||
-              histogram_quantile(%(quantile)s, sum(rate(kubelet_pleg_relist_duration_seconds_bucket{%(kubeletSelector)s}[5m])) by (%(clusterLabel)s, instance, le) * on(%(clusterLabel)s, instance) group_left(node) kubelet_node_name{%(kubeletSelector)s})
+              histogram_quantile(
+                %(quantile)s, 
+                sum(rate(kubelet_pleg_relist_duration_seconds_bucket{%(kubeletSelector)s}[5m])) by (%(clusterLabel)s, instance, le) 
+                * on(%(clusterLabel)s, instance) group_left (node) 
+                max by (%(clusterLabel)s, instance, node) (kubelet_node_name{%(kubeletSelector)s})
+              )
             ||| % ({ quantile: quantile } + $._config),
             labels: {
               quantile: quantile,