spider should suppress errors in close_connection

because stmt_da no longer expects errors at this stage,
but mysql_close() call can still hit my_error() in net_serv.cc

storage/spider/mysql-test/spider/include/clean_up_spider.inc

@@ -3,7 +3,6 @@ DROP FUNCTION spider_copy_tables;
 DROP FUNCTION spider_ping_table;
 DROP FUNCTION spider_bg_direct_sql;
 DROP FUNCTION spider_direct_sql;
---replace_regex /\.dll/.so/
 UNINSTALL SONAME IF EXISTS 'ha_spider';
 DROP TABLE IF EXISTS mysql.spider_xa;
 DROP TABLE IF EXISTS mysql.spider_xa_member;

storage/spider/spd_table.cc

@@ -6813,7 +6813,11 @@ int spider_close_connection(
   }
 
   spider_rollback(spider_hton_ptr, thd, TRUE);
+
+  Dummy_error_handler deh; // suppress network errors at this stage
+  thd->push_internal_handler(&deh);
   spider_free_trx(trx, TRUE, false);
+  thd->pop_internal_handler();
 
   DBUG_RETURN(0);
 }