Do not use an arch suffix for the coredns name

[afbjorklund]

They are using multi-arch images instead...
So don't append something like -arm64 to it.

Just use e.g. "k8s.gcr.io/coredns:1.6.5",
and Docker will pull the right platform image.

See https://hub.docker.com/r/coredns/coredns

As seen in #6007 et al

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: afbjorklund

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• OWNERS [afbjorklund]

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[codecov-io]

Codecov Report

Merging #6243 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #6243   +/-   ##
======================================
  Coverage    38.5%   38.5%           
======================================
  Files         122     122           
  Lines        8145    8145           
======================================
  Hits         3136    3136           
  Misses       4600    4600           
  Partials      409     409

Impacted Files	Coverage Δ
pkg/minikube/bootstrapper/images/kubeadm.go	96% <100%> (ø)	⬆️

[tstromberg]

/ok-to-test

[minikube-bot]

All Times minikube: [ 122.129643 126.740795 123.893050]
All Times Minikube (PR 6243): [ 125.035215 125.711807 126.940731]

Average minikube: 124.254496
Average Minikube (PR 6243): 125.895918

Averages Time Per Log

+----------------------+-----------+--------------------+
|         LOG          | MINIKUBE  | MINIKUBE (PR 6243) |
+----------------------+-----------+--------------------+
| minikube v           |  0.689353 |           0.542738 |
| Creating kvm2        | 47.559917 |          46.995472 |
| Preparing Kubernetes | 49.613814 |          51.764089 |
| Pulling images       |  3.031266 |           2.599605 |
| Launching Kubernetes | 20.546731 |          21.190348 |
| Waiting for cluster  |  2.763252 |           2.755256 |
| Done                 |           |                    |
|                      |  0.051075 |           0.045697 |
+----------------------+-----------+--------------------+

[medyagh]

@afbjorklund looks good to me also, after resolving the conflict

[minikube-pr-bot]

Error: running mkcmp: exit status 1