Delete Nodes by NodeRef and compare node and machine names when getting a Hetzner node

[xmudrii]

What this PR does / why we need it:

This PR attempts to fix the bug which occurs when a Machine is rolled-out and the new Machine has the same IP addresses as the old one. It could happen that the machine-controller sets the NodeOwner label on the old Node object to the UID of the new Machine. That can break the logic for removing the old Node object, as it depends on the NodeOwner label having the UID of the Machine that's being deleted.

There are two fixes:

• The getNode function which is used when adding the NodeRef now confirms that the instance and node names match for Hetzner Machines/instances. Previously, we only checked IP addresses, so if we a new Machine has the same addresses as the old one, it can adopt a node that's to-be-deleted
  • This assumes the name of the Node object will always be the same as the Machine name.
    • The Machine name is not always same as the Node name. For example, on AWS, the Machine name is based on the MachineDeployment name, while the Node name is the internal DNS name.
  • On providers with CCM (internal or external), that's not a problem because CCM is responsible for setting the ProviderID on the Node object. If the ProviderID is present, it will be used by the getNode function instead of IP addresses
• The deleteNodeForMachine function now uses NodeRef if it's present. We use NodeRef for all other things when deleting a machine, such as evicting the node and deleting the cloud provider instance
  • The old logic (based on the NodeOwner label) is kept in the place but it's used only as a fall-back if the NodeRef is not present

Optional Release Note:

* Delete the Node object by NodeRef if it's present
* Compare node and instances names when applying the NodeOwner label for Hetzner machines/instances

[xmudrii]

/assign @kron4eg @xrstf

[xmudrii]

/retest

[irozzo-1A]

/approve

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: irozzo-1A, xmudrii

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:

• OWNERS [irozzo-1A,xmudrii]

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

[irozzo-1A]

/lgtm

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 875072471baa1beb0bda5c2628e99d3abcea4841

[xmudrii]

/hold cancel