MDEV-15803 Fix and re-enable test galera_var_auto_inc_control_on

The test assumes that `@@global.auto_increment_offset` is equal to
`wsrep_local_index + 1`. Which is normally the case if galera runs
with option `wsrep_auto_increment_control` enabled.
However, if some prior test performs a restart of a server, then
`wsrep_local_index` may change, and galera will set the value of
`auto_increment_offset` accordingly.
However, if `auto_increment_offset` changes during a test run, then
mtr will complain. To avoid that, tests that perform restarts include
`auto_increment_offset_save.inc` and `auto_increment_offset_restore.inc`.
Which reset the value of `auto_increment_offset`. And when that
happens, `auto_increment_offset` will no longer be equal to
`wsrep_local_index + 1`, and the test fails.
To avoid this problem, simply check that the offsets are different
on the nodes that compose the cluster.

mysql-test/suite/galera/disabled.def

@@ -28,6 +28,5 @@ galera_ssl_upgrade : MDEV-13549 Galera test failures
 galera.MW-329 : wsrep_local_replays not stable
 galera.MW-328A : have_deadlocks test not stable
 galera_var_retry_autocommit : MDEV-15794 Test failure on galera.galera_var_retry_autocommit
-galera_var_auto_inc_control_on : MDEV-15803 Test failure on galera.galera_var_auto_inc_control_on
 query_cache : MDEV-15805 Test failure on galera.query_cache
 

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

 CREATE TABLE t1 (f1 INTEGER AUTO_INCREMENT PRIMARY KEY, node VARCHAR(10)) ENGINE=InnoDB;
-SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
-VARIABLE_VALUE
-2
-SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index';
-VARIABLE_VALUE
-0
 SELECT @@auto_increment_increment = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size');
 @@auto_increment_increment = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size')
 1
-SELECT @@global.auto_increment_offset = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index') + 1;
-@@global.auto_increment_offset = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index') + 1
+auto_increment_offset_differ
 1
 INSERT INTO t1 VALUES (DEFAULT, 'node1');;
 INSERT INTO t1 VALUES (DEFAULT, 'node2');;
-SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
-VARIABLE_VALUE
-2
-SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index';
-VARIABLE_VALUE
-1
 SELECT @@auto_increment_increment = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size');
 @@auto_increment_increment = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size')
 1
-SELECT @@global.auto_increment_offset = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index') + 1;
-@@global.auto_increment_offset = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index') + 1
+auto_increment_offset_differ
 1
 INSERT INTO t1 VALUES (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2');;
 INSERT INTO t1 VALUES (DEFAULT, 'node1'), (DEFAULT, 'node1'), (DEFAULT, 'node1'), (DEFAULT, 'node1'), (DEFAULT, 'node1'), (DEFAULT, 'node1'), (DEFAULT, 'node1'), (DEFAULT, 'node1'), (DEFAULT, 'node1'), (DEFAULT, 'node1');;

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

@@ -5,24 +5,21 @@
 --source include/galera_cluster.inc
 --source include/have_innodb.inc
 
-# Save original auto_increment_offset values.
---let $node_1=node_1
---let $node_2=node_2
---source include/auto_increment_offset_save.inc
-
 --connection node_1
 
 CREATE TABLE t1 (f1 INTEGER AUTO_INCREMENT PRIMARY KEY, node VARCHAR(10)) ENGINE=InnoDB;
 
+--let $auto_increment_offset_node_1 = `SELECT @@global.auto_increment_offset`
 # auto_increment_increment is equal to the number of nodes
-# auto_increment_offset is equal to the ID of the node
-
-SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
-SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index';
 SELECT @@auto_increment_increment = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size');
-SELECT @@global.auto_increment_offset = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index') + 1;
+
+--connection node_2
+--disable_query_log
+--eval SELECT @@global.auto_increment_offset != $auto_increment_offset_node_1 AS auto_increment_offset_differ;
+--enable_query_log
 
 # Expect no conflicts
+--connection node_1
 --send INSERT INTO t1 VALUES (DEFAULT, 'node1');
 
 --connection node_2
@@ -34,12 +31,18 @@ SELECT @@global.auto_increment_offset = (SELECT VARIABLE_VALUE FROM INFORMATION_
 --connection node_2
 --reap
 
-SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
-SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index';
+--let $auto_increment_offset_node_2 = `SELECT @@global.auto_increment_offset`
+# auto_increment_increment is equal to the number of nodes
 SELECT @@auto_increment_increment = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size');
-SELECT @@global.auto_increment_offset = (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_index') + 1;
+
+--connection node_1
+--disable_query_log
+--eval SELECT @@global.auto_increment_offset != $auto_increment_offset_node_2 AS auto_increment_offset_differ;
+--enable_query_log
+
 
 # Expect no conflicts
+--connection node_2
 --send INSERT INTO t1 VALUES (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2'), (DEFAULT, 'node2');
 
 --connection node_1