systemd-journal: Fix parallel build

In order to be able to build in parallel, add a $(MODULE_DEPS_LIBS) to
the appropriate _DEPENDENCIES in modules/systemd-journal/Makefile.am.
This fixes #248.

Reported-by: Peter Czanik <czanik@balabit.hu>
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>