MXS-2243_labels Maxscale system tests prepare environment by themselves

maxscale-system-test changed in order to control test environment by itself.
Every test checks which machines are running, compare with list of needed machines
and start new VMs is they are missing in the running machines list.
Tests are executiong MDBCI commands, MDBCI executable should be in the PATH

maxscale-system-test/big_load.cpp

@@ -56,7 +56,7 @@ void load(long int *new_inserts, long int *new_selects, long int *selects, long
         Test->maxscales->close_rwsplit(0);
 
         Test->tprintf("Waiting for the table to replicate\n");
-        Test->repl->sync_slaves();
+        nodes->sync_slaves();
 
         pthread_t thread1[threads_num];
         pthread_t thread2[threads_num];