Code review comment for lp:~al-maisan/launchpad/spec-job-class-503839

Hello there!

This is another step in the renovation of the (Soyuz) build farm. Now that
we're introducing additional build farm job types we need to be able to figure
out what these are without hardcoding that information.

This is mostly required by the general build farm infrastructure i.e. for the
purpose of job dispatch time estimation and candidate job selection.

Pre-implementation discussion (via email) with Gary Poster and others.

Tests to run:

    bin/test -vv -t TestJobClasses

No pertinent "make lint" errors or warnings.

Please see also bug #503839 for more detail.