chore: don't refer to hyperkube in template if > 1.16

[jackfrancis]

Reason for Change:

This PR doesn't add an unused KUBELET_IMAGE env var in the /etc/default/kubelet config file if the Kubernetes version is >= 1.17.0, because we don't support hyperkube starting with that version of k8s.

Issue Fixed:

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[codecov]

Codecov Report

Merging #2676 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2676   +/-   ##
=======================================
  Coverage   71.77%   71.77%           
=======================================
  Files         134      134           
  Lines       25071    25071           
=======================================
  Hits        17995    17995           
  Misses       6021     6021           
  Partials     1055     1055

[mboersma]

/lgtm

[acs-bot]

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