Services v2 (ip-per-service)

DO NOT COMMIT.  Needs test updates and a new e2e test.  Some FIXMEs still.  95% complete.

Add support for IP-per-service behavior.  This creates virtual IP addresses for each service, and uses iptables to route traffic "magically".

The first few commits are relatively independent, and could be extracted to different PRs, if you feel like making me suffer.

See #1107 for background.
local svc

You can also use "${svcs_to_clean[@]:0}" since Joe found out that doesn't trigger nounset on an empty array.

Also see above about `do_teardown()` without the `function` tag (nitpick.)