Run taint removal only if Kubernetes API is available

[torredil]

What is this PR about? / Why do we need it?

Currently, if K8s API client creation fails, it does so silently. Thus it is possible for k8sClient to be nil, which gets passed into NewDriver -> NewNodeService. To avoid a panic, removeTaintInBackground should only be executed if the client is available.

k8sClient, err := cfg.K8sAPIClient()
	if err != nil {
		klog.V(2).InfoS("Failed to setup k8s client")
	}

drv, err := driver.NewDriver(cloud, &options, m, md, k8sClient)

driver.node = NewNodeService(o, md, m, k)

if k != nil {
	// Remove taint from node to indicate driver startup success
	// This is done at the last possible moment to prevent race conditions or false positive removals
	time.AfterFunc(taintRemovalInitialDelay, func() {
		removeTaintInBackground(k, taintRemovalBackoff, removeNotReadyTaint)
	})
}

What testing is done?

make verify && make test

[github-actions]

Code Coverage Diff

This PR does not change the code coverage

[ConnorJC3]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ConnorJC3

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 [ConnorJC3]

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