bug#35716: Password security bugs in LUKS configuration during guided install

[sirmacik]

Hey Guix

I've asked on IRC if those bugs were known but apparently no, so here
they are:

- during guided installation with LUKS encryption one is not able to
  enter password longer then length of field;
- in the same field password is shown during typing (lets one see bug
  above, characters typed after reaching length of field are simply
  not recorded);

Field with conformation hides typed letters. Due to bug #1 I wasn't
able to check if it works properly.

--
sirmacik
PGP: 0xE0DC81D523891771