This will help with the next patch, where we wean off using a global
for features: connectd.c has access to the feature bits.
Since connectd might now want to send a message, it needs the crypto_state
non-const, which makes this less trivial than it would otherwise be.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
It's more natural than using a zero-secret when something goes wrong.
Also note that the HSM will actually kill the connection if the ECDH
fails, which is fortunately statistically unlikely.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
