Don't show netaddr if not connected.

[rustyrussell]

As I noticed in pastebin from #284

# lightning-cli getpeers
{ "peers" : 
[ 
	{ "unique_id" : 0, "state" : "CHANNELD_NORMAL", "netaddr" : "Unknown protocol 0", "peerid" : "0365c02afb409f4571d2962039c8c6e7394c93bc91a9a983c8e8b3dedbf993c8f6", "connected" : false, "channel" : "1196170:6:1", "msatoshi_to_us" : 0, "msatoshi_total" : 10000000000 },