kube-discovery: deduplicate multicast responses
kube-discovery: deduplicate multicast responses

If we get duplicate records in response to our multicast queries, we
de-duplicate before writing to /etc/hosts.

gambol99/kops,gambol99/kops,aledbf/kops,justinsb/kops,aledbf/kops,gambol99/kops,mad01/kops,blakebarnett/kops,justinsb/kops,robinpercy/kops,andrewsykim/kops,chrislovecnm/kops,justinsb/kops,robinpercy/kops,chrislovecnm/kops,tsupertramp/kops,blakebarnett/kops,kubernetes/kops,aledbf/kops,mad01/kops,chrislovecnm/kops,andrewsykim/kops,robinpercy/kops,andrewsykim/kops,blakebarnett/kops,tsupertramp/kops,gambol99/kops,kubernetes/kops,chrislovecnm/kops,tsupertramp/kops,tsupertramp/kops,aledbf/kops,kubernetes/kops,robinpercy/kops,mad01/kops,blakebarnett/kops,mad01/kops,andrewsykim/kops