Test: Provide additional control of local MaxScale

When running BLR locally, you need to be able to specify what
IP the BLR is visible at (127.0.0.1 does not work for VM nodes)
and also to perform cleanup etc. action when needed.

maxscale-system-test/testconnections.h

@@ -140,6 +140,11 @@ public:
      */
     int copy_mariadb_logs(Mariadb_nodes* repl, const char* prefix, std::vector<std::thread>& threads);
 
+    /**
+     * @brief MaxScale runs locally, specified using -l.
+     */
+    bool local_maxscale;
+
     /**
      * @brief no_backend_log_copy if true logs from backends are not copied
      *        (needed if case of Aurora RDS backend or similar)