mcelog: enable mcelog daemon mode, triggers, and use systemd
    
    Update mcelog to use daemon mode by default, fix the upstream
    triggers to actually work, enable systemd, and temporarily add
    a hack that causes mcelog to run once knowing it will fail due
    to an upstream kernel bug (first read of /dev/mcelog will fail).
    
    NOTE: as soon as upstream fixes are taken this will be cleaned up.
    
    Signed-off-by: Jon Masters <jcm@jonmasters.org>