It is possible to call `ensure_sdcard` in a way that requires only SD
card be inserted, but not necessarily formatted.
This is useful for SD-protect and possibly other use-cases where the SD
card is read-only, and "not formatted" is identical to "not containing
the right files".
It seems counterintuitive that we need to regenerate ui fixtures because
of some work on passphrase.
The reason is that we have changed where the state (now session id) is
generated. We have moved it to Features, so it is generated already
after the Initialize message is received. It used to be generated later
- during the PassphraseReq/Ack workflow and in some tests we ask for
randomness between those steps.
