[Tails-dev] Please review and merge bugfix/strict_live-persi…

Hi,

This branch fixes a bug and a typo which together made it possible for
live-persist (and hence Tails Greeter) to list LUKS-encrypted
*harddrive* partitions with GPT label "TailsData".

ticket: none
branch: bugfix/strict_live-persist_media

Candidate for Tails 0.16, merged into experimental.

87b2298 live-persist: Fix variable mismatch, fixing probe white-list.
7bae77c live-persist: Fix --media option when no devices are attached.

Cheers!