gossipd: remove time-delayed local channel_update, produce DISABLE on-demand.

We have a lot of infrastructure to delay local channel_updates to
avoid spamming on each peer reconnect; we had to keep tracking of
pending ones though, in case we needed the very latest for sending an
error when failing an HTLC.

Instead, it's far simpler to set the local_disabled flag on a channel
when we disconnect, but only send a disabling channel_update if we
actually fail an HTLC.

Note: handle_channel_update() TAKES update (due to tal_arr_dup), but we
didn't use that before.  Now we do, add annotation.

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

tests/test_pay.py

@@ -91,11 +91,13 @@ def test_pay_disconnect(node_factory, bitcoind):
     inv = l2.rpc.invoice(123000, 'test_pay_disconnect', 'description')
     rhash = inv['payment_hash']
 
+    wait_for(lambda: [c['active'] for c in l1.rpc.listchannels()['channels']] == [True, True])
+
     # Can't use `pay` since that'd notice that we can't route, due to disabling channel_update
     route = l1.rpc.getroute(l2.info['id'], 123000, 1)["route"]
 
     l2.stop()
-    l1.daemon.wait_for_log('Disabling channel .*, active 1 -> 0')
+    wait_for(lambda: [c['active'] for c in l1.rpc.listchannels()['channels']] == [False, False])
 
     # Can't pay while its offline.
     with pytest.raises(RpcError):
@@ -146,8 +148,8 @@ def test_pay_get_error_with_update(node_factory):
     l2.rpc.dev_suppress_gossip()
     l3.stop()
 
-    # Make sure that l2 has processed the local update which disables.
-    l2.daemon.wait_for_log('Received channel_update for channel {}\(.*\) now DISABLED was ACTIVE \(from apply_delayed_local_update\)'.format(chanid2))
+    # Make sure that l2 has seen disconnect, considers channel disabled.
+    wait_for(lambda: [c['active'] for c in l2.rpc.listchannels(chanid2)['channels']] == [False, False])
 
     l1.rpc.sendpay(route, inv['payment_hash'])
     with pytest.raises(RpcError, match=r'WIRE_TEMPORARY_CHANNEL_FAILURE'):