udev rules fix
    
    Resolves: bz808817
    
    use systemctl try-restart kdump.service instead of old /etc/init.d/kdump restart
    systemctl try-restart will restart kdump service only if the kdump service is runing. Original behavior is wrong when user does not chkconfig on the service.
    
    Tested the cpu online/offline events.
    
    Signed-off-by: Dave Young <dyoung@redhat.com>
    Acked-by: Vivek Goyal <vgoyal@redhat.com>