Adjust tests now that wsrep_OSU_method is a session variable.

mysql-test/suite/galera/r/galera_var_OSU_method.result

 CREATE TABLE t1 (f1 INTEGER PRIMARY KEY) Engine=InnoDB;
-SET GLOBAL wsrep_OSU_method = "RSU";
+SET SESSION wsrep_OSU_method = "RSU";
 SET DEBUG_SYNC = 'alter_table_before_open_tables WAIT_FOR continue';
 ALTER TABLE t1 ADD COLUMN f2 INTEGER;;
 SET GLOBAL wsrep_OSU_method = "TOI";

mysql-test/suite/galera/r/galera_var_OSU_method2.result

 CREATE TABLE t1 (f1 INTEGER PRIMARY KEY) Engine=InnoDB;
-SET GLOBAL wsrep_OSU_method = "TOI";
+SET SESSION wsrep_OSU_method = "TOI";
 SET DEBUG_SYNC = 'alter_table_before_open_tables WAIT_FOR continue';
 ALTER TABLE t1 ADD COLUMN f2 INTEGER;;
 SET SESSION wsrep_sync_wait = 0;

mysql-test/suite/galera/t/galera_var_OSU_method.test

@@ -10,7 +10,7 @@
 CREATE TABLE t1 (f1 INTEGER PRIMARY KEY) Engine=InnoDB;
 
 --connection node_1
-SET GLOBAL wsrep_OSU_method = "RSU";
+SET SESSION wsrep_OSU_method = "RSU";
 SET DEBUG_SYNC = 'alter_table_before_open_tables WAIT_FOR continue';
 --send ALTER TABLE t1 ADD COLUMN f2 INTEGER;
 

mysql-test/suite/galera/t/galera_var_OSU_method2.test

@@ -10,7 +10,7 @@
 CREATE TABLE t1 (f1 INTEGER PRIMARY KEY) Engine=InnoDB;
 
 --connection node_1
-SET GLOBAL wsrep_OSU_method = "TOI";
+SET SESSION wsrep_OSU_method = "TOI";
 SET DEBUG_SYNC = 'alter_table_before_open_tables WAIT_FOR continue';
 --send ALTER TABLE t1 ADD COLUMN f2 INTEGER;