This splits maybe_create_hsm_secret() in two parts (either encrypted
or in clear) for clarity, and adds an encryption detection in load_hsm().
There are actually three cases if an encryption key is passed:
- There is no hsm_secret => just create it and store the encrypted seed
- There is an encrypted hsm_secret => the provided key should be able to
decrypt the seed, if the wrong key is passed libsodium will nicely error
and hsmd will exit() to not throw a backtrace (using status_failed() as for
other errors) at the face of an user who mistyped its password.
- There is a non-encrypted hsm_secret => load the seed, delete the
hsm_secret, create the hsm_secret, store the encrypted seed.
d393cda215