Test running Tails from an external hard disk

Originally created by @sajolida on #15742 (Redmine)

From Cybelle’s June spreadsheet: https://lists.torproject.org/pipermail/tor-project/2018-July/001871.html

If we want people to rely more on Tails it might be useful to some people to install Tails on a hard disk instead of a USB stick, to have more storage capacity, be faster, and more reliable.

Related issues

• Related to #10731 (closed)
• Related to #8422
• Related to #6397
• Blocks #16080 (closed)