prevent kube-proxy trying to change nf_conntrack_max

[prezha]

fixes #11418

an example of the error is given in the description of issue #11418

as detailed in kubernetes-sigs/kind#2240 (comment) and in kubernetes-sigs/kind#2241, as of kernel 5.12.2, kube-proxy will fail while trying to set nf_conntrack_max parameter

this can be avoided by explicitly telling kube-proxy to leave it as-is - ie, passing maxPerCore parameter with value 0 via kubeadm config template
ref: https://kubernetes.io/docs/reference/config-api/kube-proxy-config.v1alpha1/#kubeproxy-config-k8s-io-v1alpha1-KubeProxyConntrackConfiguration

[prezha]

/ok-to-test

[k8s-ci-robot]

@prezha: The following test failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
pull-minikube-build	f425739	link	/test pull-minikube-build

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[minikube-pr-bot]

kvm2 driver with docker runtime

+----------------+----------+---------------------+
|    COMMAND     | MINIKUBE | MINIKUBE (PR 11419) |
+----------------+----------+---------------------+
| minikube start | 50.1s    | 49.1s               |
| enable ingress | 34.4s    | 34.4s               |
+----------------+----------+---------------------+

Times for minikube start: 47.5s 47.0s 55.2s 53.0s 47.8s
Times for minikube (PR 11419) start: 47.4s 47.4s 46.8s 48.6s 55.2s

Times for minikube ingress: 34.4s 34.2s 34.2s 34.7s 34.3s
Times for minikube (PR 11419) ingress: 34.2s 33.7s 33.8s 33.8s 36.7s

docker driver with docker runtime

+----------------+----------+---------------------+
|    COMMAND     | MINIKUBE | MINIKUBE (PR 11419) |
+----------------+----------+---------------------+
| minikube start | 21.5s    | 21.6s               |
| enable ingress | 30.1s    | 30.8s               |
+----------------+----------+---------------------+

Times for minikube ingress: 28.5s 29.0s 31.5s 29.5s 32.0s
Times for minikube (PR 11419) ingress: 30.0s 27.5s 36.5s 30.5s 29.5s

Times for minikube start: 21.1s 22.1s 21.1s 21.8s 21.5s
Times for minikube (PR 11419) start: 21.6s 22.1s 21.9s 20.9s 21.3s

docker driver with containerd runtime

+----------------+----------+---------------------+
|    COMMAND     | MINIKUBE | MINIKUBE (PR 11419) |
+----------------+----------+---------------------+
| minikube start | 44.8s    | 43.8s               |
| enable ingress |          |                     |
+----------------+----------+---------------------+

Times for minikube start: 46.3s 43.1s 43.6s 46.6s 44.5s
Times for minikube (PR 11419) start: 42.3s 47.0s 43.1s 43.2s 43.2s

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: medyagh, prezha, spowelljr

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