Logs are mixed into the same files

[rettigs]

As of v2 of this cookbook, all the logs that are usually in /var/log/rdiff-backup/www.example.com_-var-www (for example) now end up in /var/log/rdiff-backup/_var_www, so finding host-specific logs is difficult since they are all mixed together.

To be more specific, every host that has a job to back up /var/www (for example) is logging to the same file (/var/log/rdiff-backup/_var_www/2015-11.log), and the stdout/stderr lines are intermingled with those of the other backups.