rancher-cloudprovider: Improve node group discovery

[ctrox]

Which component this PR applies to?

cluster-autoscaler

What type of PR is this?

/kind bug

What this PR does / why we need it:

Previsouly the rancher provider tried to parse the node spec.providerID to extract the node group name. Instead, we now get the machines by the node name and then use a rancher specific label that should always be on the machine. This should work more reliably for all the different node drivers that rancher supports.

Which issue(s) this PR fixes:

Fixes #5140

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.:

[x13n]

/lgtm

Although for changes like this I think it would make more sense to uncomment entries in your OWNERS file, so that rancher-specific changes can be reviewed & approved by the people listed there.

[ctrox]

Agreed, but aren't OWNERS required to be members of the Kubernetes org? If so, I guess I'm looking for 2 sponsors ;)

[ctrox]

/assign @towca

[x13n]

Ah, good point. I guess after reviewing this PR I could qualify as one. You'd still need someone else, from another company.

[mwielgus]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ctrox, mwielgus

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

The pull request process is described here

Needs approval from an approver in each of these files:

• cluster-autoscaler/OWNERS [mwielgus]

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