Restore original value of wsrep_on after waiting for sync point.

Author: temeo

mysql-test/include/galera_wait_sync_point.inc

@@ -1,5 +1,6 @@
-let $wait_timeout = 10;
+--let $wait_timeout = 10
+--let $wsrep_on_orig = `SELECT @@wsrep_on`
 SET SESSION wsrep_on = 0;
 --let $wait_condition = SELECT 1 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_debug_sync_waiters' AND VARIABLE_VALUE = '$galera_sync_point'
 --source include/wait_condition.inc
-SET SESSION wsrep_on = 1;
+--eval SET SESSION wsrep_on = $wsrep_on_orig