feat: update sql proxy offline log

Author: caojiajun

lb-driver/src/main/java/com/netease/nim/lbd/ConnectionManager.java

@@ -545,8 +545,10 @@ private void removeSqlProxy(List<SqlProxy> list) {
                         continue;
                     }
                     //标记下线
-                    pool.setOffline();
-                    logger.info("sql proxy = {} offline", sqlProxy);
+                    if (pool.isOnline()) {
+                        pool.setOffline();
+                        logger.info("sql proxy = {} offline", sqlProxy);
+                    }
                     //直接关闭空闲连接
                     while (true) {
                         RealConnection connection2Close = pool.getConnection2Close();