chore!: Default ListenerClass externalTrafficPolicy to null

[sbernauer]

Description

Part of stackabletech/issues#770
Blocked by kube-rs/kube#1821
Currently produces an invalid CRD because of this

As we start actually using LoadBalancers, we need to make sure they work everywhere.
@Maleware actually run into this in stackabletech/hbase-operator#698

Definition of Done Checklist

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Author

• Changes are OpenShift compatible
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