closes https://github.com/TryGhost/Toolbox/issues/525
- When the update check is run as an offloaded job (in a worker thread) the errors that are handled over "logger.error" do not get bubbled up to the job manager to be handled fully. With an optional "rethrowErrors" flag it's not possible to throw errors when the update check is run as a "job" and handle as usual when run in the main thread (through the admin route trigger)