executor/Srgt Hartman: be explicit about the ignored states + vivian integration tests
Rather than having to select which states produce jobs, let's instead
ignore the specific states that are not supposed to generate a job,
namely IDLE
and REGISTRATION_FAILED
.
This way, when we add new states and forget to handle them, it will lead to a nice exception, instead of just... nothing.
Fixes: 502e1919 ("executor/Sergent Hartman: turn registration failures into their own state")