Make functional-tester deploy easy

[gyuho]

Current functional-tester deployment requires a lot of dependencies (iptables, tc, go), which makes it hard to deploy or containerize. We should make this easier so that community can run with other cloud providers.

First step is introduce low-overhead proxy layer #9081 to get rid of iptables dependency. And then put tester components in a single container image to make distribution much easier and faster. Once we get rid of iptables dependency, we can even run the same set of tests in a single VM, rather than spawning 6-separate VMs.

[gyuho]

Now iptables or tc dependency is replaced by bridge layer. Once etcd-io/gofail#14 gets resolved, everything can be run locally.