- 优化 CheckAvailable retry 重试一次；

FreeSql/Internal/ObjectPool/ObjectPool.cs

@@ -116,6 +116,15 @@ namespace FreeSql.Internal.ObjectPool
                         
                         try
                         {
+                            try
+                            {
+                                Policy.OnCheckAvailable(conn);
+                                break;
+                            }
+                            catch
+                            {
+                                conn.ResetValue();
+                            }
                             if (Policy.OnCheckAvailable(conn) == false) throw new Exception(CoreStrings.Available_Thrown_Exception("CheckAvailable"));
                             break;
                         }