fix: 修改获取系统用户认证信息时username的选择逻辑；（单独设置过的系统用户认证信息登录资产失败）

apps/assets/models/user.py

@@ -248,13 +248,16 @@ class SystemUser(BaseUser):
         if user_id:
             user = get_object_or_none(User, pk=user_id)
 
+        _username = self.username
         if self.username_same_with_user:
             if user and not username:
-                username = user.username
+                _username = user.username
+            else:
+                _username = username
 
         # 加载某个资产的特殊配置认证信息
         try:
-            self.load_asset_special_auth(asset, username)
+            self.load_asset_special_auth(asset, _username)
         except Exception as e:
             logger.error('Load special auth Error: ', e)
             pass