sd_check_events() is called asynchronously, and might race
with device removal. So always take a disk reference when
processing the event to avoid the device being removed while
the event is processed.
Signed-off-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Ewan D. Milne <emilne@redhat.com> Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>