We push a huge msg for listchannels with the million-channels project.
We need to fix that, but this works around it so we can benchmark.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Format is "le16 len; u8 message[len]" same as wire format specified in
BOLTs, even though the endian conversion is overkill for local messages.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>