fix: do not use return in updating kubelet node labels

[AbelHu]

What type of PR is this?
/kind bug

What this PR does / why we need it:

fixes a bug in Add-KubeletNodeLabel where the log content is added to the return value by Write-Log, causing KubeletNodeLabels to contain unexpected content which ends preventing kubelet from starting:

                                       "NodeLabels":  [
                                                          "2024-10-23T18:24:39.6797661+00:00: adding label kubernetes.azure.com/kubelet-serving-ca=cluster to kubelet node labels...",
                                                          "agentpool=npwin,kubernetes.azure.com/agentpool=npwin,agentpool=npwin,kubernetes.azure.com/agentpool=npwin,kubernetes.azure.com/cluster=MC_cameissebld106479871_wintester_eastus2,kubernetes.azure.com/consolidated-additional-properties=a3253cd6-916b-11ef-a610-6643c19b51dd,kubernetes.azure.com/kubelet-identity-client-id=78f4691a-f952-4bd3-83c0-0869e2821eed,kubernetes.azure.com/mode=user,kubernetes.azure.com/node-image-version=AKSWindows-2022-containerd-20348.2762.241009,kubernetes.azure.com/nodepool-type=VirtualMachineScaleSets,kubernetes.azure.com/os-sku=Windows2022,kubernetes.azure.com/role=agent,kubernetes.azure.com/storageprofile=managed,kubernetes.azure.com/storagetier=Premium_LRS,storageprofile=managed,storagetier=Premium_LRS,kubernetes.azure.com/kubelet-serving-ca=cluster"

...

Exception calling "RunProcess" with "3" argument(s): "Cannot process request because the process (992) has exited."
At C:\k\kubeletstart.ps1:106 char:1
+ [RunProcess.exec]::RunProcess($exe, $args, [System.Diagnostics.Proces ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : InvalidOperationException

Which issue(s) this PR fixes:

Fixes #

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Special notes for your reviewer:

Release note:

none