Support multiple, comma-separated --dns-cluster-ip values

[ajohnstone]

Issue #, if available:
#1684

Description of changes:
Support a comma separated list rather than a single scalar value.
bootstrap.sh will override clusterDNS in the kubelet config.

Use case:

This will allow enabling IPVS and node-local by first having node-local and then fall back to the service ip for coredns.

Refer to docs:
https://kubernetes.io/docs/tasks/administer-cluster/nodelocaldns/

If using kube-proxy in IPVS mode, --cluster-dns flag to kubelet needs to be modified to use that NodeLocal DNSCache is listening on. Otherwise, there is no need to modify the value of the --cluster-dns flag, since NodeLocal DNSCache listens on both the kube-dns service IP as well as .

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Testing Done
Modified bootstrap and executed on a re-run.
Tests pass, should these not be part of the build workflow?

+ [[ 0 -eq 0 ]]
+ echo '✅ ✅ All Tests Passed! ✅ ✅'
✅ ✅ All Tests Passed! ✅ ✅
+ exit 0

[cartermckinnon]

Sounds reasonable to me. The linter found an extra space that needs to be removed, @ajohnstone

[ajohnstone]

@cartermckinnon thanks removed extra whitespace :)

[ajohnstone]

@cartermckinnon mind triggering the tests and approval thanks :)

[cartermckinnon]

/ci

[github-actions]

@cartermckinnon roger that! I've dispatched a workflow. 👍

[github-actions]

@cartermckinnon the workflow that you requested has completed. 🎉

AMI variant	Build	Test
1.23 / al2	success ✅	success ✅
1.23 / al2023	success ✅	success ✅
1.24 / al2	success ✅	success ✅
1.24 / al2023	success ✅	success ✅
1.25 / al2	success ✅	success ✅
1.25 / al2023	success ✅	success ✅
1.26 / al2	success ✅	success ✅
1.26 / al2023	success ✅	success ✅
1.27 / al2	success ✅	success ✅
1.27 / al2023	success ✅	success ✅
1.28 / al2	success ✅	success ✅
1.28 / al2023	success ✅	success ✅
1.29 / al2	success ✅	success ✅
1.29 / al2023	success ✅	success ✅