Add Check resolv.conf is empty to avoid CoreDNS crash

[yankay]

What type of PR is this?

/kind feature

What this PR does / why we need it:

If the /etc/resolv.conf is empty. The kubernetes coredns is in CrashLoopBackOff status with "no nameservers found" error.

The same issue is at:

• https://serverfault.com/questions/1081685/kubernetes-coredns-is-in-crashloopbackoff-status-with-no-nameservers-found-err
• https://discuss.kubernetes.io/t/coredns-is-in-crashloopbackoff-state-with-no-nameservers-found-error-log/17863

Which issue(s) this PR fixes:

Fixes #9497 (workaround)

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Add Check resolv.conf is empty to avoid CoreDNS crash

[yankay]

HI @oomichi @floryut , would you please review the PR ?
Thanks :-)

[oomichi]

That seems unrelated test failure like:

    TASK [container-engine/cri-o : Remove legacy CRI-O kubic apt repo key] *********
    Monday 28 November 2022  03:37:23 +0000 (0:00:00.049)       0:00:45.250 *******
    skipping: [almalinux8]
    skipping: [fedora]
fatal: [ubuntu20]: FAILED! => {"changed": false, "msg": "Failed to download key at https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable/xUbuntu_20.04/Release.key: HTTP Error 404: Not Found"}
fatal: [debian10]: FAILED! => {"changed": false, "msg": "Failed to download key at https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable/Debian_10/Release.key: HTTP Error 404: Not Found"}

[oomichi]

Thanks for updating.

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: oomichi, yankay

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[yankay]

That seems unrelated test failure like:

    TASK [container-engine/cri-o : Remove legacy CRI-O kubic apt repo key] *********
    Monday 28 November 2022  03:37:23 +0000 (0:00:00.049)       0:00:45.250 *******
    skipping: [almalinux8]
    skipping: [fedora]
fatal: [ubuntu20]: FAILED! => {"changed": false, "msg": "Failed to download key at https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable/xUbuntu_20.04/Release.key: HTTP Error 404: Not Found"}
fatal: [debian10]: FAILED! => {"changed": false, "msg": "Failed to download key at https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable/Debian_10/Release.key: HTTP Error 404: Not Found"}

HI @oomichi

There is the PR to fix the issue. #9525.
Welcome to review it :-)

[yankay]

HI @floryut,
would you please review the PR :-)

[dougsland]

looks sane to me even not seeing it in my env.
/lgtm

[yankay]

Thanks @oomichi @dougsland for the PR review.