(WIP) Change Service module to conforms task interface.
Log skipped subtasks in service module.
Change service module to log every subtask.
Change yum service to conforms task interface.
Do logging in each module, not in task.RunOneTask().
Use result.ExecCommand instead of executil.Run in user and group modules.
Change Chown and Chmod to conforms task interface. Let Directory module
use Chown module internally.
Remove now unused code.