- refactor running the command into a helper function,
to deal with the regular if-command-failed-then-complain pattern.
- mark parameters as unused.
- move distinction about kind of DBus file up into the MachineIdJob
and remove the enum that marked it.
- Testing some of the functionality that's been added just now:
- copyfile fails, buggy implementation
- poolsize fails, buggy implementation
- removefile not tested
