Make memory erasure feature compatible with overlayfs
The “Erasure of the overlayfs read-write branch on shutdown” test
scenario fails. But interestingly, “Tails erases memory on DVD boot
medium removal: overlayfs read-write branch” passes. Looks like
live-boot behaves slightly differently on overlayfs than on aufs,
which seems to explain why mountpoints are not visible and can’t be
unmounted and thus cleaned.
Parent Task: #8415
Related issues
Original created by @intrigeri on 15146 (Redmine)