Certification failure for table having unique key

[Henrik Torelm]

Galera cluster (with two nodes) is failing to commit due to certification failure on table having unique key.

Steps to reproduce:

1) Setup Galera cluster (MySQL 5.6 with wsrep patch, galera provider version 2 or 3) on two nodes
2) Create database "test"
3) Load schema and data to the database from "test_2013-11-27.sql"
4) Run query files (different!) simultaneously on both servers

Run at server 1:
mysql -u root test < query101_1.sql

Run at server 2:
mysql -u root test < query102_1.sql

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Expected: no errors/failures

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Experienced:
Failure in mysql.err:

2013-11-27 12:37:48 25742 [Note] WSREP: cluster conflict due to certification failure for threads:
2013-11-27 12:37:48 25742 [Note] WSREP: Victim thread:
   THD: 180, mode: local, state: executing, conflict: cert failure, seqno: 722967
   SQL: commit

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Observations:

Issue (failure) does not appear in following cases:
1) Drop unique key;
2) Run both query files at one of servers (locally, simultaneously).

Note that none of the rows in table are updated from more than one node i.e. same row is not updated from both nodes.
But, same row updated more than once on same node.

Attached instructions to reproduce, schema and testdata