This looked like a test flake, but was real:
```
l1.daemon.wait_for_log("closing soon due to the funding outpoint being spent")
# We won't gossip the dead channel any more (but we still propagate node_announcement). But connectd is not explicitly synced, so wait for "a bit".
time.sleep(1)
> assert len(get_gossip(l1)) == 2
E assert 4 == 2
```
We can see that two channel_updates come in *after* we mark it dying:
```
gossipd: channel 103x1x0 closing soon due to the funding outpoint being spent
gossipd: REPLY WIRE_GOSSIPD_NEW_BLOCKHEIGHT_REPLY with 0 fds
022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-gossipd: Received channel_update for channel 103x1x0/0 now DISABLED
022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-gossipd: Received channel_update for channel 103x1x0/1 now DISABLED
```
We should keep marking channel_updates the same way.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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