Memory erasure freezes more often on Stretch

Originally created by @intrigeri on #11730 (Redmine)

We’ve seen this happen in the automated persistence tests.

Attachments

• tails-stretch-memory-erasure-to-busybox.png
• memory-erasure-failure.png
• 01_59_03_Tails_shuts_down_on_USB_boot_medium_removal.png
• 02_12_45_Installing_Tails_to_a_USB_drive_with_an_MBR_partition_table_but_no_partitions,_and_making_sure_that_it_boots.png

Related issues

• Is duplicate of #11786 (closed)