Fix nodePlugin affinity not propagating from OperatorConfig to DaemonSet

[ksc98]

Describe what this PR does

When using the ceph-csi-operator with Rook, node affinity configured in the OperatorConfig's driverSpecDefaults.nodePlugin.affinity is ignored.

The CSI nodeplugin DaemonSet runs on all nodes regardless of the configured affinity rules.

Root cause: Rook's operator creates Driver CRs with a non-nil but empty Affinity struct:

Affinity: &corev1.Affinity{
    NodeAffinity: getNodeAffinity(pluginNodeAffinityEnv, &corev1.NodeAffinity{}),
}

The mergeDriverSpecs() function only checks if dest.Affinity == nil before merging defaults from OperatorConfig. Since the Affinity pointer is an empty struct (never nil!), the merge never happens.

Example Scenario

In my cluster, there are some nodes that won't ever run pods that need Ceph PVCs. If we don't run a DaemonSet on these nodes, we can free up some requests, which is especially beneficial for smaller nodes.

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Fixes: #issue_number

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[Madhu-1]

@ksc98 can we please fix this in Rook to keep it nil if it does not need to be set?

[ksc98]

@ksc98 can we please fix this in Rook to keep it nil if it does not need to be set?

I can definitely raise a PR there instead. Thanks for taking a look!

[ksc98]

Hi @Madhu-1, just wanted to let you know that the issue I'm describing was actually fixed in this PR (#346), which unfortunately landed just one week after the v0.4.1 (current) release!

#346

the node plugin and other Daemon sets should use the affinity specified in the driver. Example: role=storage-node where non storage-node(s) don't require the node plugin

Weirdly, the rook operator has the code to correctly create the OperatorConfig. it was added in 9d298fe

So all set here, nothing needed besides my waiting for the next release :P