Comment 5 for bug 1863145

> Dimitri - we can look to do that for future, but that doesn't address the upgrade issue. Did something change that made this break?

Almost certainly my change to ensure flash-kernel always runs on upgrade (as it's the subject of a trigger, and trigger invocations are lost on package upgrade which results in all sorts of fun with u-boot and the migration of boot configurations on pi for the .4 release).

I'll add a check to ensure flash-kernel dies quietly in the case it finds itself in a container.