DNF on different column is not pushing down to I_S

The second query is not pushing down

```
mysql> explain select * from information_schema.tables where table_name = 'a';
+----------------+----------+------+---------------+------------------+
| id | estRows | task | access object | operator info |
+----------------+----------+------+---------------+------------------+
| MemTableScan_5 | 10000.00 | root | table:TABLES | table_name:["a"] |
+----------------+----------+------+---------------+------------------+
1 row in set (0.01 sec)

mysql> explain select * from information_schema.tables where table_name = 'a' or table_schema = 'b';
+----------------------+----------+------+---------------+------------------------------------------+
| id | estRows | task | access object | operator info |
+----------------------+----------+------+---------------+------------------------------------------+
| Selection_5 | 8000.00 | root | | or(eq(Column#3, "a"), eq(Column#2, "b")) |
| └─MemTableScan_6 | 10000.00 | root | table:TABLES | |
+----------------------+----------+------+---------------+------------------------------------------+
2 rows in set (0.00 sec)
```