assert that number of pods on node does not exceed CIDR address range

The number of pods on a given node is determined by the  --max-pods=k
directive. When the address space is exhausted, no more pods can be
scheduled even if from the --max-pods-perspective, the node still has
capacity.

The special case that a pod is scheduled and uses the node IP in the
host network namespace is too "soft" to derive a guarantee.

Comparing kubelet_max_pods with kube_network_node_prefix when given
allows to assert that pod limits match the CIDR address space.

roles/kubernetes/node/defaults/main.yml

@@ -71,6 +71,10 @@ kube_apiserver_node_port_range: "30000-32767"
 
 kubelet_load_modules: false
 
+# Configure the amount of pods able to run on single node
+# default is equal to application default
+kubelet_max_pods: 110
+
 ## Support custom flags to be passed to kubelet
 kubelet_custom_flags: []