feat: report both old and new styles of node OS information

[allxiao]

spec.template.spec.nodeSelector[beta.kubernetes.io/os]: deprecated since v1.14; use "kubernetes.io/os" instead

To maintain compatibility, the virtual node should declare both styles of OS information, so that the Pod being scheduled to the virtual node can choose any of the following options

• use the legacy style beta.kubernetes.io/os nodeSelector
• migrate to use the new kubernetes.io/os nodeSelector before the beta one is dropped completely from API server

Currently, we only report beta.kubernetes.io/os, which will block the users from working on the nodeSelector migration.

[codecov-commenter]

Codecov Report

Merging #479 (8715d35) into master (0c76852) will increase coverage by 1.11%.
The diff coverage is 49.70%.

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@@            Coverage Diff             @@
##           master     #479      +/-   ##
==========================================
+ Coverage   42.91%   44.02%   +1.11%     
==========================================
  Files          50       50              
  Lines        5735     5944     +209     
==========================================
+ Hits         2461     2617     +156     
- Misses       3017     3071      +54     
+ Partials      257      256       -1     

Impacted Files	Coverage Δ
pkg/featureflag/feature_flag.go	75.00% <ø> (+20.00%)	⬆️
pkg/network/aci_network.go	20.43% <7.74%> (-6.10%)	⬇️
pkg/auth/auth.go	60.32% <44.68%> (-6.35%)	⬇️
pkg/metrics/metrics.go	75.18% <57.14%> (-1.56%)	⬇️
pkg/provider/aci.go	44.59% <65.85%> (+10.70%)	⬆️
pkg/provider/aci_volumes.go	45.19% <70.58%> (ø)
pkg/provider/containergroup_to_pod.go	71.93% <75.80%> (-3.35%)	⬇️
pkg/analytics/analytics.go	64.70% <100.00%> (ø)
pkg/provider/vk_node.go	88.67% <100.00%> (+0.56%)	⬆️
provider/aci.go	37.97% <100.00%> (+0.19%)	⬆️
... and 5 more

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[Fei-Guo]

I'd rather go with just "beta.kubernetes.io/os" label, the current k8s API version of VK is still low.

[allxiao]

Hi @Fei-Guo

The beta.kubernetes.io/os label was deprecated since v1.14. Now the K8s API version for VK is 1.19. I think we should follow the deprecation process to add the support for the kubernetes.io/os label.

The labels on node defines the capabilities for a node. When we are in such kind of label deprecation, the node should declare it supports both labels for best compatibility, so that the users who want to schedule pods to VK can choose any one of the following:

1. use the legacy beta.kubernetes.io/os nodeSelector
2. migrate to use the kubernetes.io/os nodeSelector before the beta one is removed completely

When we only provide beta.kubernetes.io/os, the second one won't work, which blocks the user from preparing for the label deprecation and removal.

[Fei-Guo]

Thanks. I think the "beta.kubernetes.io/os" label already exists in vNode object. We just miss the ""kubernetes.io/os" label.
It seems the node-cli does update the label
https://github.com/virtual-kubelet/node-cli/blob/85167f75d00837452dbd6efe6e51512cdc65615e/internal/commands/root/node.go#L62

Since Heba is working on remove node cli dependency from azure-aci repo and I think she can add the new label in the change.
@helayoty.

[helayoty]

@allxiao may I ask you to rebase your PR?

[helayoty]

lgtm