While tracing it's useful to know not just when a transaction is committed but also when one is aborted. So add a trace event for transaction aborts. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>