MXS-2900 Rename maxscale-system-test directory to system-test

A link with the old directory name is provided.

system-test/long_insert_sql/test_init.sql

@@ -0,0 +1,4 @@
+CREATE DATABASE IF NOT EXISTS test;
+USE test;
+DROP TABLE IF EXISTS test_bind_fetch;
+CREATE TABLE test_bind_fetch(c1 char(10), c2 text);