getLocalDetector() used to pass a utiliptables.Interface to
NewDetectLocalByCIDR() so that NewDetectLocalByCIDR() could verify
that the passed-in CIDR was of the same family as the iptables
interface. It would make more sense for getLocalDetector() to verify
this itself and just *not call NewDetectLocalByCIDR* if the families
don't match, and that's what the code does now. So there's no longer
any need to pass the utiliptables.Interface to the local detector.
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