client-go PortForwarder: don't log an error if net.Listen fails

[yvespp]

What this PR does / why we need it:
If ipv6 is disabled the client-go PortForwarder logs an error:

E0406 17:26:06.983609   29625 portforward.go:209] Unable to create listener: Error listen tcp6 [::1]:30143: socket: address family not supported by protocol

This pull request removes this error log. Reasons:

• Tunnel creation might still succeed on ipv4 and the error just confuses the user (see helm error: Unable to create listener: Error listen tcp6  helm/helm#2223).
• If the tunnel can't be created the error gets also loggen in listenOnPort.
• runtime.HandleError should only be used on errors "when a non-user facing piece of code cannot return an error" which isn't the case here.

Which issue this PR fixes
Fixes helm/helm#2223

[k8s-ci-robot]

Hi @yvespp. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with @k8s-bot ok to test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.

[k8s-reviewable]

This change is 

[grodrigues3]

@k8s-bot ok to test

[deads2k]

/lgtm

[k8s-github-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: deads2k, yvespp

Needs approval from an approver in each of these OWNERS Files:

• staging/src/k8s.io/client-go/OWNERS [deads2k]

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[k8s-github-robot]

Automatic merge from submit-queue