A small problem when rehashing catalog cache

Hi,

When we search catalog cache, we move the searched tuple to the front of the list:

```
		/*
		 * We found a match in the cache.  Move it to the front of the list
		 * for its hashbucket, in order to speed subsequent searches.  (The
		 * most frequently accessed elements in any hashbucket will tend to be
		 * near the front of the hashbucket's list.)
		 */
		dlist_move_head(bucket, &ct->cache_elem);
```

If I understand correctly, we reverse the list in RehashCatCache() and RehashCatCacheLists():

```
	/* Move all entries from old hash table to new. */
	for (i = 0; i < cp->cc_nbuckets; i++)
	{
		dlist_mutable_iter iter;

		dlist_foreach_modify(iter, &cp->cc_bucket[i])
		{
			CatCTup    *ct = dlist_container(CatCTup, cache_elem, iter.cur);
			int			hashIndex = HASH_INDEX(ct->hash_value, newnbuckets);

			dlist_delete(iter.cur);
			dlist_push_head(&newbucket[hashIndex], &ct->cache_elem);
		}
	}
```

Maybe "dlist_push_head" -> "dlist_push_tail"? Thoughts?

--
Regards,
ChangAo Chen