Request GTID replication in tests that require it

Added the required calls to request GTID replication in the mysqlmon
failover tests.

maxscale-system-test/mysqlmon_failover_rejoin_old_slave.cpp

@@ -198,6 +198,7 @@ void run(TestConnections& test)
 
 int main(int argc, char* argv[])
 {
+    Mariadb_nodes::require_gtid(true);
     TestConnections test(argc, argv);
 
     run(test);