Update Azure VM Images to enable DHCP on eth0 instead of using Azures IMDS endpoint

[nawazkh]

/kind feature

Describe the solution you'd like
[A clear and concise description of what you want to happen.]

• Enabling the "fallback option of DHCP on eth0 instead of using default Azure's IMDS endpoint" will help users to assign the extra IPConfigs on the host to the scheduled pods.
  • Azure's IMDS endpoint was enabled since Ubuntu 18.04 and it was disabled in AKS engine due to ubuntu-18.04 distro + AzureCNI results in OS Provisioning Timeouts (OSPTO) Azure/aks-engine#761.
  • A user can create extra IPConfigs via Support for configurable Network Interfaces #2411.
  • For the extra IPs to be assigned to the scheduled pods, user should use a CNI such as Azure CNI.
• This issue aims to make the change in the image-builder repo for the Azure VMs to support the above use case.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

• Accomplishes a part of Add support & documentation on using Azure CNI with capz #467

Environment:

• cluster-api-provider-azure version: n/a
• Kubernetes version: (use kubectl version): n/a
• OS (e.g. from /etc/os-release): Ubuntu

[nawazkh]

/assign

[nawazkh]

A PR is already in works for this kubernetes-sigs/image-builder#1090. I am working on adding a goss tests to test the changes exclusive to Azure VMs

[nawazkh]

kubernetes-sigs/image-builder#1090 has merged. 🎉
/close

[k8s-ci-robot]

@nawazkh: Closing this issue.

In response to this:

kubernetes-sigs/image-builder#1090 has merged. 🎉
/close

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