fix: use pre-defined relays for autorelay

Unfortunately, we don't currently have any way to pick out good relays from bad.
That means we keep searching, trying bad relays, searching some more, trying
_the same relays_, etc. until we randomly find 3 good stable relays. In
practice, this means we just keep searching forever and keep thrashing the DHT.

see libp2p/go-libp2p#694

core/node/libp2p/relay.go

@@ -21,4 +21,4 @@ func Relay(disable, enableHop bool) func() (opts Libp2pOpts, err error) {
 	}
 }
 
-var AutoRealy = simpleOpt(libp2p.EnableAutoRelay())
+var AutoRealy = simpleOpt(libp2p.ChainOptions(libp2p.EnableAutoRelay(), libp2p.DefaultStaticRelays()))