Add vars for dnsmasq/kubedns apps memory limits and replica counts

[bogdando]

With large deploys, like 1000 nodes or so, kubedns default memory limit and replicas of 1 might become a bottleneck, as well as those for the dnsmasq daemon set (see https://github.com/kubernetes-incubator/kargo/blob/master/docs/dns-stack.md for details).

Those should be expressed as inventory vars.