Stop timeout before fixing replication

The timeout is hit very often if the cluster fixing takes some time. This
causes false positives so the timeout should be stopped before attempting
to fix the cluster.

maxscale-system-test/avro.cpp

@@ -87,6 +87,7 @@ int main(int argc, char *argv[])
     }
 
     execute_query(test.repl->nodes[0], "DROP TABLE test.t1;RESET MASTER");
+    test.stop_timeout();
     test.repl->fix_replication();
 
     return test.global_result;