contained cni: rename default cni file to have higher priority

[medyagh]

fixes #7874

on old ISO :

$ ls /etc/cni/net.d/
k8s.conf

but on the new ISO we have

$ ls /etc/cni/net.d/
87-podman-bridge.conflist  k8s.conf

related to the podman cni ISO change 4803589
what was happening, is because the podman cni was alphabetically higher importance for containerd and was picked up by it

[k8s-ci-robot]

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[medyagh]

/ok-to-test

[minikube-pr-bot]

kvm2 Driver
Times for minikube: [65.622549277 66.966693308 66.23466939]
Average time for minikube: 66.274637325

Times for Minikube (PR 7875): [71.30005041000001 66.36498926899999 66.82536656299999]
Average time for Minikube (PR 7875): 68.16346874733334

Averages Time Per Log

+--------------------------------+-----------+--------------------+
|              LOG               | MINIKUBE  | MINIKUBE (PR 7875) |
+--------------------------------+-----------+--------------------+
| * minikube v1.10.0-beta.1 on   |  0.062662 |           0.063978 |
| Debian 9.11                    |           |                    |
| * Using the kvm2 driver based  |  0.021569 |           0.020226 |
| on existing profile            |           |                    |
| * Starting control plane node  |  0.006700 |           0.003316 |
| minikube in cluster minikube   |           |                    |
| * Creating kvm2 VM (CPUs=2,    | 40.445085 |          43.035895 |
| Memory=3700MB, Disk=20000MB)   |           |                    |
| ...                            |           |                    |
| * Preparing Kubernetes v1.18.0 | 23.512028 |          22.827760 |
| on Docker 19.03.8 ...          |           |                    |
| * Verifying Kubernetes         |  1.498903 |           1.425231 |
| components...                  |           |                    |
| * Enabled addons:              |  0.637953 |           0.699185 |
| default-storageclass,          |           |                    |
| storage-provisioner            |           |                    |
| * Done! kubectl is now         |  0.086330 |           0.083904 |
| configured to use "minikube"   |           |                    |
|                                |  0.003408 |           0.003975 |
+--------------------------------+-----------+--------------------+

docker Driver
Times for minikube: [26.962441878 27.326434826 27.149537873]
Average time for minikube: 27.146138192333336

Times for Minikube (PR 7875): [27.098500969000003 26.969104834000003 27.887147014]
Average time for Minikube (PR 7875): 27.318250939000006

Averages Time Per Log

+----------------------------------------+-----------+--------------------+
|                  LOG                   | MINIKUBE  | MINIKUBE (PR 7875) |
+----------------------------------------+-----------+--------------------+
| * minikube v1.10.0-beta.1 on           |  0.074326 |           0.075405 |
| Debian 9.11                            |           |                    |
| * Using the docker driver              |  0.002653 |           0.002735 |
| based on existing profile              |           |                    |
| * Starting control plane node          |  0.059767 |           0.061103 |
| minikube in cluster minikube           |           |                    |
| * Creating docker container            |  7.812444 |           7.809512 |
| (CPUs=2, Memory=3700MB) ...            |           |                    |
| * Preparing Kubernetes v1.18.0         |  0.000225 |           0.000247 |
| on Docker 19.03.2 ...                  |           |                    |
|   -                                    | 18.198363 |          17.815137 |
| kubeadm.pod-network-cidr=10.244.0.0/16 |           |                    |
| * Verifying Kubernetes                 |  0.815558 |           1.482174 |
| components...                          |           |                    |
| * Enabled addons:                      |  0.114514 |           0.002738 |
| default-storageclass,                  |           |                    |
| storage-provisioner                    |           |                    |
| * Done! kubectl is now                 |  0.065245 |           0.065807 |
| configured to use "minikube"           |           |                    |
|                                        |  0.003042 |           0.003390 |
+----------------------------------------+-----------+--------------------+