refs codership/mysql-wsrep#31

- Removes useless call to wsrep_xid_init() in wsrep_apply_events().
  Transaction's xid is already initialized at that point.
- Adds call to wsrep_set_SE_checkpoint() for committing TOI events
  in the applier side.
- Includes test case that reproduced the issue.

mysql-test/suite/galera/r/mysql-wsrep#31.result

@@ -0,0 +1,10 @@
+CREATE TABLE t1 (f1 CHAR(255)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES('test');
+CREATE DATABASE db;
+Shutting down server 2 ...
+Recovering server 2 ...
+Performing --wsrep-recover ...
+Restarting server ...
+Using --wsrep-start-position when starting mysqld ...
+DROP TABLE t1;
+DROP DATABASE db;