Chroot browsers don't work when Tails is manually installed with YUMI

If YUMI is used to manually install Tails, the chrooted browsers (unsafe-browser, i2p-browser) will not work.

amnesia@amnesia:~$ sudo unsafe-browser
* Setting up chroot
/usr/local/sbin/unsafe-browser: 53: /usr/local/sbin/unsafe-browser: cannot open /lib/live/mount/medium/live/Tails.module: No such file
mount: mount point /var/lib/unsafe-browser/chroot/proc does not exist
unsafe-browser: error: Failed to setup chroot.

The problem in this case is that after installing Tails with YUMI, /lib/live/mount/medium/live/Tails.module is located at /lib/live/mount/medium/multiboot/tails-i386-1.3.1/live/Tails.module which cannot work.

The manual instructions for Windows (https://tails.boum.org/doc/first_steps/installation/manual/windows/index.en.html) say to use Universal USB Installer. Perhaps we should document (somewhere) that YUMI (http://www.pendrivelinux.com/yumi-multiboot-usb-creator/) should not be used.

(And/Or) perhaps there could be a refactoring done—as long as it wouldn’t be too painful or too hackish—so that $blah/live/Tails.module will work regardless of the value of $blah.

Related issues

• Related to #6871 (closed)

Original created by @kytv on 9115 (Redmine)