a-a-g-machine-id: add systemd's machine id

The dmidecode based algorithm may not work on all architectures.

man machine-id

Related to rhbz#1140044

Signed-off-by: Jakub Filak <jfilak@redhat.com>
testsuite: add sanity test for a-a-g-machine-id

Related to rhbz#1140044

Signed-off-by: Jakub Filak <jfilak@redhat.com>
a-a-g-machine-id: suppress its failures in abrt_event.conf

If an event script exits with a non-zero code, abrtd deletes entire dump
directory.

Failures of a-a-g-machine-id must not lead to the deletion of a dump
directory.

Related to rhbz#1140044

Signed-off-by: Jakub Filak <jfilak@redhat.com>