Fix: ignore not a VMSS error for VMAS nodes in reconcileBackendPools

[CecileRobertMichon]

What type of PR is this?

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/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

/kind bug

What this PR does / why we need it: This fixes an issue with UpdateLoadBalancer where if a new VMAS node joins a cluster in "vmss" vmType, UpdateLoadBalancer fails with "not a vmss instance". Instead, getting the nodeName via VMAS which allows the reconcile LB to proceed and the node does get added successfully.

To repro: add expose a service type load balancer, then add a node of type VM and watch UpdateLoadBalancer fail.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Release note:

ignore not a VMSS error for VMAS nodes in reconcileBackendPools

[CecileRobertMichon]

will fix the unit test tomorrow

[nilo19]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CecileRobertMichon, nilo19

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