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Add initial availability zones support for Azure nodes
**What this PR does / why we need it**:
The first part of [Azure Availability Zone feature](https://github.com/kubernetes/features/issues/586).
This PR adds initial availability zone (AZ) support for Azure nodes. With this PR, Azure nodes with AZ will have label `failure-domain.beta.kubernetes.io/zone=<region>-<zoneID>`, e.g. `southeastasia-1`.
It also updates instance metadata api-version to 2017-12-01, which is required for AZ.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #
**Special notes for your reviewer**:
VirtualMachineScaleSetVM doesn't have AZ info yet. It will be supported later after new Azure Go SDK releases.
**Release note**:
```release-note
Azure nodes with availability zone now will have label `failure-domain.beta.kubernetes.io/zone=<region>-<zoneID>`.
```
/kind feature
/sig azure
/assign @brendandburns @khenidak @andyzhangx
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