Use `pkg/discovery` to provide nodes discovery between daemon instances.
The functionality is driven by two different command-line flags: the
experimental `--cluster-store` (previously `--kv-store`) and
`--cluster-advertise`. It can be used in two ways by interested
components:
1. Externally by calling the `/info` API and examining the cluster store
field. The `pkg/discovery` package can then be used to hit the same
endpoint and watch for appearing or disappearing nodes. That is the
method that will for example be used by Swarm.
2. Internally by using the `Daemon.discoveryWatcher` instance. That is
the method that will for example be used by libnetwork.
Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>
