Guidance for systems that do not have the ability to rollback #256
Description
The programming model for the FIrmware Update API assumes that the system will always reboot back to a point where the FWU API can be queried to determine the FWU state of the system compoments.
Although this is technically true from the point of view that this model is describing the view presented by the Update service to the Update client via calls to the API - and therefore there is no "FWU state" that is relevant to the specification if the system fails to boot the firmware (i.e. the device is 'bricked', or the device boots some alternative recovery firmware).
This possiblity is mentioned in 4.6 Bootloader operation, under §4.6.4.
It would be helpful for the earlier sections on State transitions, Volatile states, and Behavior on error to mention scenarios where the system fails to restart and thus never complete a state transition.