Enable abrt-journal-core.service by default
This is a follow up to 0706049913b0c5b3f300cb46426009e97f3318df.
Disabling abrt-ccpp.service resulted in ABRT not working, because I
incorrectly thought ABRT's systemd integration was handled by
abrt-vmcore.service, which we already have enabled. It is not: it is
handled by abrt-journal-core.service. It is great that coredumpctl now
works, but we want ABRT to continue to work as well, so enable the
required service.
Note that https://bugzilla.redhat.com/show_bug.cgi?id=1419980 needs to
be fixed as well, or SELinux disabled, for this to work.
https://fedoraproject.org/wiki/Changes/coredumpctl
Signed-off-by: Michael Catanzaro <mcatanzaro@gnome.org>