Trigger emergency shutdown on resume when the boot device is missing

i.e. it was removed during suspend. The idea is that when suspended, both sequences of user actions should result in emergency shutdown:

wake up the system, then unplug the boot device: this works
unplug the boot device, then wake up the system: this used to work but the fix for #11729 (closed) broke it as a side effect

See #11052-note_31 and follow-ups.

Original created by @intrigeri on 16787 (Redmine)

Edited Nov 22, 2019 by intrigeri

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