/distribution/beaker/setup: tidy up logging

Also changed the single-host case to not run both code paths in
parallel, since that would often break beakerlib's journal (which is
apparently not multiprocess-safe).

Change-Id: I54926789ca26a977aea549e2a5d43b914d9e324e
Merge "/distribution/beaker/setup: tidy up logging" into develop