fix bug for spider where using "not like"

test case:
t1 is a spider engine table;
CREATE TABLE `t1` (
`id` int(11) NOT NULL DEFAULT '0',
`name` char(64) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=SPIDER

query: "select * from t1 where name not like 'x%' " would dispatch "select xxx name name like 'x%' " to remote mysqld, is wrong