peer: commit outstanding changes before sending PKT_CLOSE.

Pierre points out that we don't handle this, and it can happen due
to race; the spec says we are not supposed to send PKT_CLOSE with
uncommitted changes.

Closes: #29
Reported-by: Pierre-Marie Padiou
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

daemon/peer.c

@@ -1529,6 +1529,10 @@ static bool peer_start_shutdown(struct peer *peer)
 	enum state newstate;
 	u8 *redeemscript;
 
+	/* We might have uncommited changes; if so, commit them now. */
+	if (!do_commit(peer, NULL))
+		return false;
+
 	db_start_transaction(peer);
 
 	db_begin_shutdown(peer);