Disambiguate "id" column in People query which joins Email

Summary: We end up with both "user.id" and "email.id". Disambiguate for ORDER.

Test Plan: Ran Conduit user.query query with "email".

Reviewers: wez, chad

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D6234

src/applications/people/query/PhabricatorPeopleQuery.php

@@ -242,4 +242,8 @@ final class PhabricatorPeopleQuery
     return $this->formatWhereClause($where);
   }
 
+  protected function getPagingColumn() {
+    return 'user.id';
+  }
+
 }