Parallel replication deadlock victim preference code errorneously removed

Somewhere during the work on VATS in InnoDB, the code that calls thd_deadlock_victim_preference() was errorneously removed; and later the function itself was also removed errorneously as dead code.

commit 2fd3af44830e8df9d60f2e8a955f9ed17e744986

Author: sensssz <hjmsens@gmail.com>

Date:   Thu Dec 1 13:45:23 2016 -0500

    MDEV-11168: InnoDB: Failing assertion: !other_lock || wsrep_thd_is_BF(lock->trx->mysql_thd, FALSE) || wsrep_thd_is_BF(other_lock->trx->mysql_thd, FALSE)

commit 1513630d302932a90c94fef6803877f37f0e0f22

Author: Eugene Kosov <claprix@yandex.ru>

Date:   Mon Apr 9 17:21:21 2018 +0300

    remove dead code

This may lead to significantly more transaction retries in in-order parallel replication, since InnoDB may choose the wrong deadlock victim (If T1 and T2 need to replicate in-order and deadlock with each other, then choosing T1 as deadlock victim is pointless as T2 will be killed and deadlocked anyway by parallel replication).

The lost code should be restored.
It looks like the InnoDB deadlock code in later MariaDB versions was changed substantially, so the restored code probably needs to be rewritten for merging to those later versions.