router: Specify sinceIndex for etcd watch

If we don’t specify this, etcd assumes we want the *next* update, not everything since index 0.

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
router: Copy and close TCP listener before returning it to the pool

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
router: Add test mode that uses real discoverd/etcd

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>