MXS-1476: Add test case

Test for MXS-1476 that checks that the behavior is what is
expected. Currently, the test passes as behavior is what is expected.

maxscale-system-test/mxs1476.cpp

@@ -0,0 +1,63 @@
+/**
+ * MXS-1476: priority value ignored when a Galera node rejoins with a lower wsrep_local_index than current master
+ *
+ * https://jira.mariadb.org/browse/MXS-1476
+ */
+
+#include "testconnections.h"
+
+void do_test(TestConnections& test, int master, int slave)
+{
+    test.connect_maxscale();
+    test.try_query(test.conn_rwsplit, "DROP TABLE IF EXISTS test.t1");
+    test.try_query(test.conn_rwsplit, "CREATE TABLE test.t1 (id int)");
+    test.try_query(test.conn_rwsplit, "INSERT INTO test.t1 VALUES (1)");
+
+    test.tprintf("Block a slave node and perform an insert");
+    test.galera->block_node(slave);
+    sleep(5);
+    test.try_query(test.conn_rwsplit, "INSERT INTO test.t1 VALUES (1)");
+
+    test.tprintf("Unblock the slave node and perform another insert");
+    test.galera->unblock_node(slave);
+    sleep(5);
+    test.try_query(test.conn_rwsplit, "INSERT INTO test.t1 VALUES (1)");
+    test.close_maxscale_connections();
+
+    test.tprintf("Block the master node and perform an insert");
+    test.galera->block_node(master);
+    sleep(5);
+    test.connect_maxscale();
+    test.try_query(test.conn_rwsplit, "INSERT INTO test.t1 VALUES (1)");
+
+    test.tprintf("Unblock the master node and perform another insert (expecting failure)");
+    test.galera->unblock_node(master);
+    sleep(5);
+    test.add_result(execute_query_silent(test.conn_rwsplit, "INSERT INTO test.t1 VALUES (1)") == 0, "Query should fail");
+    test.close_maxscale_connections();
+
+    test.connect_maxscale();
+    test.try_query(test.conn_rwsplit, "DROP TABLE test.t1");
+}
+
+int main(int argc, char** argv)
+{
+    TestConnections test(argc, argv);
+    test.galera->stop_node(2);
+    test.galera->stop_node(3);
+
+    do_test(test, 1, 0);
+
+    test.tprintf("Swap the priorities around and run the test again");
+    test.ssh_maxscale(true, "sed -i 's/priority=1/priority=3/' /etc/maxscale.cnf;"
+                      "sed -i 's/priority=2/priority=1/' /etc/maxscale.cnf;"
+                      "sed -i 's/priority=3/priority=2/' /etc/maxscale.cnf;");
+    test.restart_maxscale();
+
+    do_test(test, 0, 1);
+
+    test.galera->start_node(2, "");
+    test.galera->start_node(3, "");
+    test.galera->fix_replication();
+    return test.global_result;
+}