Correct reraising of exception

When an exception was caught and rethrown, it should call 'raise' 
without any arguments because it shows the place where an exception 
occured initially instead of place where the exception re-raised

Change-Id: If613ca3521d04cda91b69e009a28e0da2357d4ff

vitrage/common/file_utils.py

@@ -26,9 +26,9 @@ def load_files(dir_path,
                with_exception=False):
     try:
         loaded_files = os.listdir(dir_path)
-    except Exception as e:
+    except Exception:
         if with_exception:
-            raise e
+            raise
         else:
             return []
     if suffix:
@@ -56,7 +56,7 @@ def load_yaml_file(full_path, with_exception=False):
             return yaml.load(stream, Loader=yaml.BaseLoader)
         except Exception as e:
             if with_exception:
-                raise e
+                raise
             else:
                 LOG.error("Fails to parse file: %s. %s" % (full_path, e))
                 return None