Fix for MDEV-12247:

If a statement with open (read only) cursor is executed there is no buffered
result set (result set rows will be fetched directly from server), so we need to skip reading unbuffered result sets if a cursor is open.

unittest/libmariadb/bulk1.c

@@ -402,6 +402,7 @@ static int bulk5(MYSQL *mysql)
 
   res= mysql_store_result(mysql);
   rows= (unsigned long)mysql_num_rows(res);
+  diag("rows: %d", rows);
   mysql_free_result(res);
 
   FAIL_IF(rows != 5, "expected 5 rows");