VMSS Flex Support: Add a new vmType for pure VMSS Flex cluster to bypass the node type check

[zmyzheng]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Currently, the CCM first checks the node type then chooses the correct VMSet implementation for the corresponding operation. It mantains a cache for the ndoe type and refreshes the cache by calling an Azure API every time the cache expires. In pure vmssflex node cluster, the node type check can be bypassed to reduce the API calls to Azure.

Which issue(s) this PR fixes:

Fixes #639

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[netlify[bot]]

✅ Deploy Preview for kubernetes-sigs-cloud-provide-azure canceled.

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[k8s-ci-robot]

Hi @zmyzheng. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[coveralls]

Coverage decreased (-0.01%) to 79.909% when pulling 4ebdb52b6957c2731eba4d1f9a02c5203b283384 on zmyzheng:vmssflex-vmtype into 8d0fb7ff4243b06d77bfb1e3d60317bc5c5f2f4e on kubernetes-sigs:master.

[andyzhangx]

/ok-to-test

[zmyzheng]

/retest

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: feiskyer, zmyzheng

The full list of commands accepted by this bot can be found here.

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Needs approval from an approver in each of these files:

• ~~OWNERS~~ [feiskyer]

Approvers can indicate their approval by writing /approve in a comment Approvers can cancel approval by writing /approve cancel in a comment

[zmyzheng]

/retest

[zmyzheng]

/retest