since DevStack is now using systemd, we can leverage that when setting
up callback_plugin used by Ansible started by ansble-deploy driver.
This patch adds two more options to the ironic_log callback plugin
configuration file - use_journal and use_syslog.
When set, they will override respective values from ironic config.
The callback plugin config is set to force usage of journald by default
in the devstack plugin.
Change-Id: I5c788dd6621c95a28aecc727a3988ad4f101b2a8
47d5e7a7b9