Fix AKS (AzureManagedCluster) cluster create on release-0.5

[jackfrancis]

/kind bug

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What steps did you take and what happened:
[A clear and concise description of what the bug is.]

The release-0.5 branch has a broken AKS implementation. At least the following PRs will need to be manually cherry-picked in order to restore functionality:

• Use region specific API calls with VMSS #1850
• use aks-managed-poolName also for vmss match #2025

What did you expect to happen:

Anything else you would like to add:
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Environment:

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

[jackfrancis]

/assign

[CecileRobertMichon]

@jackfrancis I can do a manual cherry pick directly in #2028 since there is a merge conflict

[CecileRobertMichon]

/close

fixed in #2028

[k8s-ci-robot]

@CecileRobertMichon: Closing this issue.

In response to this:

/close

fixed in #2028

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