This simplifies things, and means it's always in the database. Our
previous approach to creating it on the fly had holes when it was
created for onchaind, causing us to use another every time we
restarted.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We always hand in "NULL" (which means use tal_len on the msg), except
for two places which do that manually for no good reason.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>