When testing my model with tools/test.py, my config will be messed up…

… by the "--save-preds" option. (#2052)

* fix tools/test.py

* fix tools/test.py

* Update tools/test.py

---------

Co-authored-by: Tong Gao <gaotongxiao@gmail.com>

tools/test.py

@@ -121,6 +121,11 @@ def main():
         if isinstance(cfg.test_evaluator, (list, tuple)):
             cfg.test_evaluator = list(cfg.test_evaluator)
             cfg.test_evaluator.append(dump_metric)
+        elif isinstance(cfg.test_evaluator, dict):
+            if 'metrics' in cfg.test_evaluator:
+                cfg.test_evaluator['metrics'].append(dump_metric)
+            else:
+                cfg.test_evaluator['metrics'] = [dump_metric]
         else:
             cfg.test_evaluator = [cfg.test_evaluator, dump_metric]