Automatic merge from submit-queue (batch tested with PRs 36990, 37494, 38152, 37561, 38136)
Never set hairpin mode on every interface
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**What this PR does / why we need it**:
Abandon setting hairpin mode if finding the peer interface fails; simply return an error.
There are many reasons why finding the peer could fail - "`ethtool` not installed" is popular. Going ahead and changing the hairpin setting on every bridge-connected interface on the machine may have unwanted effects on other things installed on the machine (e.g. https://github.com/kubernetes/kops/issues/879)
**Which issue this PR fixes** : fixes#19766
**Special notes for your reviewer**:
**Release note**:
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```release-note
Kubelet will no longer set hairpin mode on every interface on the machine when an error occurs in setting up hairpin for a specific interface.
```
/cc @thockin who appears to have requested this implementation at https://github.com/kubernetes/kubernetes/pull/13628#issuecomment-138128180
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