fix: enable dhcpv6 only for ubuntu 16.04

[aramase]

Reason for Change:

• dhcpv6 systemd unit is only required for ubuntu 16.04

Issue Fixed:

Credit Where Due:

Does this change contain code from or inspired by another project?

• No
• Yes

If "Yes," did you notify that project's maintainers and provide attribution?

• No
• Yes

Requirements:

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

Notes:

[codecov]

Codecov Report

Merging #4017 (3492e5a) into master (c309c3f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4017   +/-   ##
=======================================
  Coverage   73.69%   73.69%           
=======================================
  Files         147      147           
  Lines       23164    23164           
=======================================
  Hits        17070    17070           
  Misses       4979     4979           
  Partials     1115     1115           

Impacted Files	Coverage Δ
pkg/engine/templates_generated.go	48.97% <ø> (ø)

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[aramase]

@jackfrancis What are your thoughts on enabling dualstack api model for e2e tests? The e2e test suite should work as is for dualstack. Once dualstack is beta in k/k we can add dualstack specific tests to the e2e suite.

[jackfrancis]

@jackfrancis What are your thoughts on enabling dualstack api model for e2e tests? The e2e test suite should work as is for dualstack. Once dualstack is beta in k/k we can add dualstack specific tests to the e2e suite.

Good idea. Should we add a config to the test/e2e/test_cluster_configs/ directory that looks something like examples/dualstack/kubernetes.json? FYI the JSON config is a bit different for the jenkins configs under test/e2e/test_cluster_configs/ (the actual API model goes into a "apiModel"` object, for example).

[aramase]

Good idea. Should we add a config to the test/e2e/test_cluster_configs/ directory that looks something like examples/dualstack/kubernetes.json? FYI the JSON config is a bit different for the jenkins configs under test/e2e/test_cluster_configs/ (the actual API model goes into a "apiModel"` object, for example).

I'm going to update the examples/dualstack/kubernetes.json to use 1.20 when it's available because dualstack services has been reimplemented in 1.20. The current config we use for testing is https://github.com/aramase/manifests/blob/main/dualstack/iptables-kubenet.json.

Let me add to test/e2e/test_cluster_configs.

[jackfrancis]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aramase, jackfrancis

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