This is a little more awkward, as we used to do some work
synchronously (the init message), but it's still pretty clear.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We have some duplication in handling queues, so this is an attempt at
deduplicating some of that work. `daemon_conn` now uses the
`msg_queue` and `channeld` was also migrated to `msg_queue`. At the
same time I made `msg_queue` create a copy of the messages or takes
over messages marked with `take()`. This should make cleaning up
messages easier.
