Add a missing key on DrydockLease

Summary: Depends on D18734. See PHI176. We run this query on the main Drydock lease web UI, among other places. There is currently no `status` key which can satisfy it.

Test Plan:
Viewed Drydock lease page to get the query.

Ran ##explain SELECT * FROM `drydock_lease` WHERE (status IN ('pending', 'acquired', 'active')) ORDER BY `id` DESC LIMIT 101;## before and after the change.

I don't have a ton of leases locally so the un-key'd EXPLAIN isn't //that// bad, but still shows that we're getting a better key. Before:

```
mysql> explain SELECT * FROM `drydock_lease` WHERE (status IN ('pending', 'acquired', 'active')) ORDER BY `id` DESC LIMIT 101;
+----+-------------+---------------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table         | type  | possible_keys | key     | key_len | ref  | rows | Extra       |
+----+-------------+---------------+-------+---------------+---------+---------+------+------+-------------+
|  1 | SIMPLE      | drydock_lease | index | NULL          | PRIMARY | 4       | NULL |  101 | Using where |
+----+-------------+---------------+-------+---------------+---------+---------+------+------+-------------+
1 row in set (0.00 sec)
```

After:

```
mysql> explain SELECT * FROM `drydock_lease` WHERE (status IN ('pending', 'acquired', 'active')) ORDER BY `id` DESC LIMIT 101;
+----+-------------+---------------+-------+---------------+------------+---------+------+------+---------------------------------------+
| id | select_type | table         | type  | possible_keys | key        | key_len | ref  | rows | Extra                                 |
+----+-------------+---------------+-------+---------------+------------+---------+------+------+---------------------------------------+
|  1 | SIMPLE      | drydock_lease | range | key_status    | key_status | 130     | NULL |    5 | Using index condition; Using filesort |
+----+-------------+---------------+-------+---------------+------------+---------+------+------+---------------------------------------+
1 row in set (0.00 sec)
```

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Differential Revision: https://secure.phabricator.com/D18735

src/applications/drydock/storage/DrydockLease.php

@@ -83,6 +83,9 @@ final class DrydockLease extends DrydockDAO
         'key_resource' => array(
           'columns' => array('resourcePHID', 'status'),
         ),
+        'key_status' => array(
+          'columns' => array('status'),
+        ),
       ),
     ) + parent::getConfiguration();
   }