bug#19190: Cannot boot with encrypted root

[Duncan Keall]

Thanks for the update, Ludovic!

I've just tested another install with a fresh image from master, using
as similar setup as possible to before.

The boot process still fails at mounting the root filesystem (as
expected):

  fsck.ext4: No such file or directory while trying to open /dev/mapper/main
  Possibly non-existent device?

However I found that cryptsetup was missing from the store during the
early-boot REPL, so I wasn't able to test manually mounting the
encrypted filesystem. 

Nothing in the commit history since v0.8 jumped out as being
responsible, so I'm assuming I've missed something obvious during
install. I'll have to keep looking!