[BUG] exclude not honored when node_slice_size enabled

[jpsn123]

Describe the bug
Hi Whereabouts maintainers,

We are using Whereabouts IPAM with Multus NetworkAttachmentDefinition. When enabling NodeSlice / Fast IPAM (fast_ipam: true with node_slice_size), the exclude list seems to be ignored (or not applied consistently). IPs that are explicitly excluded are still being allocated.