test-commandserver: change way of triggering early crash Future patches will move the logging facility out of the server class, so cmdserver.log can't be (ab)used for this purpose. Instead, let's hook the factory function to raise exception.

loggingutil: add basic logger backends These classes will be used in command server. They are similar to the blackboxlogger, but it can't be factored out since the blackbox is so tightly coupled with a repo object.