Return early when node name is empty

[cemakd]

This allows node driver to avoid an unnecessary 15 second startup delay when node name flag isn't set.

What type of PR is this?

/kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes #2200

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

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[sunnylovestiramisu]

Will this cause log spamming in the issue's case? Because they will not be specifying nodeName, and we will log the error. Can you confirm that the error will only get log once, and will not spam the logging?

[sunnylovestiramisu]

/test pull-gcp-compute-persistent-disk-csi-driver-e2e-arm

[k8s-ci-robot]

@cemakd: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-gcp-compute-persistent-disk-csi-driver-e2e-arm	bc308be	link	false	/test pull-gcp-compute-persistent-disk-csi-driver-e2e-arm

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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