UEFI boot tests fail on Jenkins

Once #10720 (closed) is workaround’ed, “Booting Tails from a USB drive in UEFI mode” always fail with a black screen.

Feature Branch: test/11583-uefi-boot-is-fragile-stretch

Parent Task: #10288

Original created by @intrigeri on 11583 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information