lightningd/peer_control: don't create peer struct until we've connected.

We currently create a peer struct, then complete handshake to find out
who it is.  This means we have a half-formed peer, and worse: if it's
a reconnect we get two peers the same.

Add an explicit 'struct connection' for the handshake phase, and
construct a 'struct peer' once that's done.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_lightningd.py

@@ -193,8 +193,6 @@ class LightningDTests(BaseLightningDTests):
         assert p2['state'] == 'GOSSIPING'
 
         # It should have gone through these steps
-        print(p1['log'])
-        assert 'state: HANDSHAKING -> INITIALIZING' in p1['log']
         assert 'state: INITIALIZING -> GOSSIPING' in p1['log']
 
         # Both should still be owned by gossip