API server is now dual stack capable, listening on both
IPv4 and IPv6 endpoints.
Merge pull request #224 from dimitern/apiserver-listens-dualstack

state/apiserver: Ensure we always listen to IPv4+IPv6

API server is now dual stack (IPv4+IPv6) capable, as it
listens on both 127.0.0.1 and ::1, and clients can connect
to it using both protocols. Added tests and some internal
details needed tweaking. Live tested on EC2.