Enable info log for failing tests

The three tests appear to hang in unexpected places. Enabling the info log
should reveal where the hang happens.

maxscale-system-test/mxs1824_double_cursor.cpp

@@ -58,6 +58,7 @@ int main(int argc, char** argv)
 {
     TestConnections test(argc, argv);
 
+    test.maxscales->ssh_node_f(0, true, "maxadmin enable log-priority info");
     test.maxscales->connect();
     double_cursor(test, test.maxscales->conn_rwsplit[0]);
     test.maxscales->disconnect();