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Currently the `--label-filter` flag can only be used to filter CRDs
which match the label selector passed through that flag. This change
extends the functionality to the Ingress, Service and Openshift Route
type objects. When the flag is not specified the default value is
`labels.Everything()` which is an empty string, the same as before.
Annotation based filter is inefficient because the filtering has to be
done in the controller instead of the API server like with label
filtering.