Add missing indexes to DrydockRepositoryOperation

Summary: See PHI1885. Repository operations are queryable by state and author, but neither column has a usable key. Add usable keys.

Test Plan: Ran EXPLAIN on a state query. Ran `bin/storage upgrade`. Ran EXPLAIN again, saw query go from a table scan to a `const` key lookup.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Differential Revision: https://secure.phabricator.com/D21465

src/applications/drydock/storage/DrydockRepositoryOperation.php

@@ -55,6 +55,12 @@ final class DrydockRepositoryOperation extends DrydockDAO
         'key_repository' => array(
           'columns' => array('repositoryPHID', 'operationState'),
         ),
+        'key_state' => array(
+          'columns' => array('operationState'),
+        ),
+        'key_author' => array(
+          'columns' => array('authorPHID', 'operationState'),
+        ),
       ),
     ) + parent::getConfiguration();
   }