This stage allows to configure a systemd-journald
config drop-in file located in
`/usr/lib/systemd/journald.conf.d`.
Currently it supports the following options for
the 'Journal' section: Storage, Compress, SplitMode,
MaxFileSec, MaxRetentionSec, SyncIntervalSec, Audit.
Signed-off-by: Irene Diez <idiez@redhat.com>