text: Title: Ensure /etc/hosts has a header always - Fix conformance test
  Body: We have 2 scenarios where we copy /etc/hosts
  - with host network (we just copy the /etc/hosts from node)
  - without host network (create a fresh /etc/hosts from pod info)
  
  We are having trouble figuring out whether a /etc/hosts in a
  pod/container has been "fixed-up" or not. And whether we used
  host network or a fresh /etc/hosts in the various ways we start
  up the tests which are:
  
  - VM/box against a remote cluster
  - As a container inside the k8s cluster
  - DIND scenario in CI where test runs inside a managed container
  
  Please see previous mis-guided attempt to fix this problem at
  ba20e63446815f8bcab4fc4c6e07eab2e2a9e121 In this commit we revert
  the code from there as well.
  
  So we should make sure:
  - we always add a header if we touched the file
  - we add slightly different headers so we can figure out if we used the
    host network or not.
  
  Update the test case to inject /etc/hosts from node to another path
  (/etc/hosts-original) as well and use that to compare.
  
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  **What this PR does / why we need it**:
  
  **Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
  Fixes #
  
  **Special notes for your reviewer**:
  
  **Release note**:
  <!--  Write your release note:
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  ```release-note
  Rework Kubelet set `/etc/hosts` behavior to fix conformance testability
  ```
  