[DO NOT MERGE][AKS] Add new api model

[zqingqing1]

This checklist is used to make sure that common issues in a pull request are addressed. This will expedite the process of getting your pull request merged and avoid extra work on your part to fix issues discovered during the review process.

PR information

• The title of the PR is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• Except for special cases involving multiple contributors, the PR is started from a fork of the main repository, not a branch.
• If applicable, the PR references the bug/issue that it fixes.
• Swagger files are correctly named (e.g. the api-version in the path should match the api-version in the spec).

Quality of Swagger

• I have read the contribution guidelines.
• My spec meets the review criteria:
  • The spec conforms to the Swagger 2.0 specification.
  • The spec follows the guidelines described in the Swagger checklist document.
  • Validation tools were run on swagger spec(s) and have all been fixed in this PR.

[AutorestCI]

Automation for azure-sdk-for-python

A PR has been created for you:
Azure/azure-sdk-for-python#3121

[AutorestCI]

Automation for azure-sdk-for-node

A PR has been created for you based on this PR content.

Once this PR will be merged, content will be added to your service PR:
Azure/azure-sdk-for-node#3304

[AutorestCI]

Automation for azure-sdk-for-java

Nothing to generate for azure-sdk-for-java

[AutorestCI]

Automation for azure-sdk-for-ruby

Nothing to generate for azure-sdk-for-ruby

[zqingqing1]

Just copy and paste the 2018-03-31 api model and rename it to 2018-03-31-preview.

[AutorestCI]

Automation for azure-sdk-for-go

A PR has been created for you:
Azure/azure-sdk-for-go#2571

[azuresdkci]

Can one of the admins verify this patch?

[dsgouda]

Please use x-ms-enum instead

[JackQuincy]

We have actually stopped reading this from the customer. We just default to always use VMSS for this api version, on creates, old clusters we treat as not changing from what they are. So we should be able to remove this from the schema.

[dsgouda]

Please check these properties for readonly ness

[zqingqing1]

The value should be passed by customer, and default value is nil. so we are good here

[zqingqing1]

Please don't merge before I do some test. Will let you final review when this PR is ready.

[dsgouda]

Hi @zqingqing1 will close this PR by EOW if there is no activity.

[zqingqing1]

Please don't close this PR, There is still some work from Laurent to support multi-api, after then, This PR should be good to merge.

[dsgouda]

@zqingqing1 You can always open a new PR when you are ready to go. We do not recommend keeping PRs open against the repo for too long.

[dsgouda]

Closing PR due to inactivity.
@zqingqing1 Please open a new PR when you are ready and reference this PR so we can expedite it for you