I noticed the following in logs for tests/test_connection.py::test_feerate_stress:
```
DEBUG 022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-chan#1: Failing HTLC 18446744073709551615 due to peer death
DEBUG 022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-chan#1: local_routing_failure: 8194 (WIRE_TEMPORARY_NODE_FAILURE)
```
This is because it reports the (transient) node_failure error, because
our channel_failure message is incomplete. Fix this wart up.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>