Add tests with big backend

Basic tests can be executed with 15 machines Master/slave backend. Tests have label BIG_REPL_BACKEND Default template modified to support big backend. Tests temporaraly labeled as UNSTABLE to prevent their execution nightly

maxscale-system-test/non_native_setup.cpp

@@ -26,10 +26,7 @@ int main(int argc, char* argv[])
         std::string(" ") +
         std::string(argv[1]);
 
-    int local_argc = argc - 1;
-    char** local_argv = &argv[1];
-
-    TestConnections test(local_argc, local_argv);
+    TestConnections test(argc, argv);
     sleep(3);
     setenv("src_dir", test_dir, 1);