Fix handling of service comments in iptables

[odinuge]

What type of PR is this?
/kind bug

What this PR does / why we need it:
Stumbled upon this when debugging some network issues with debian buster (ref. #71305, hopefully we can get that sorted out soon).

This will make "appendServiceCommentLocked" do what it looks like it
does. The current implementation is just plain dead code, as the
append func does not edit in place.

As discussed in the original PR, we could create a new flag to allow the
user to enable the comments when needed. This will increase the size of
the iptables rules, but not the way they work.

Original PR:
#65755

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:
Guess we can rewrite the func to something like this, if that is preferable:

func (proxier *Proxier) serviceCommentLocked(svcName string) []string {
  if proxier.endpointChainsNumber > endpointChainsNumberThreshold {
    return []string{}
  }
  return []string{"-m", "comment", "--comment", svcName}
}

Do we need a release note for this? 🤔

Does this PR introduce a user-facing change?:

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[odinuge]

/cc thockin
/cc wojtek-t

[fejta-bot]

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[danwinship]

/assign @thockin

[thockin]

Thanks!

/lgtm
/approve

[odinuge]

/retest

[odinuge]

/retest

[odinuge]

/test pull-kubernetes-e2e-gce

[odinuge]

Had to update some tests that was created after this PR. Should be good to go again now. @thockin

[aojea]

I think that the commits should we squashed so the new functionality and the tests merge together in one commit

[thockin]

Thanks!

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: odinuge, thockin

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[thockin]

#81886 includes this and is already squashed and approved (and doesn't rename the service port, which I just noticed)