Fix a bad query in LeaseQuery

Summary: Fixes T3610. This got un-scoped at some point, and is only used in Drydock so it escaped notice.

Test Plan: Ran `bin/drydock lease --type host` without hitting an exception about incorrect query construction.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T3610

Differential Revision: https://secure.phabricator.com/D6552