AppArmor: Allow logging to the Journal

Didcot will get the Journal as its stdout/stderr when it is launched
by Canterbury, or as a systemd user service.

Signed-off-by: Simon McVittie <smcv@collabora.com>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D6223