Fix intermittent test-only sort order bug.
Fix intermittent test-only sort order bug.

Lucy breaks ties by doc_id, but the test did not.  The bug only manifested
once every few hundred iterations because the collisions between scores
occurred rarely.

nwellnhof/lucy,kidaa/lucy,apache/lucy,rbevers/lucy,pombredanne/apache-lucy,nwellnhof/lucy,rbevers/lucy,apache/lucy,kidaa/lucy,rectang/lucy,kidaa/lucy,apache/lucy,kidaa/lucy,pombredanne/apache-lucy,kidaa/lucy,rbevers/lucy,kidaa/lucy,pombredanne/apache-lucy,pombredanne/apache-lucy,apache/lucy,rbevers/lucy,rbevers/lucy,nwellnhof/lucy,rbevers/lucy,rectang/lucy,rectang/lucy,pombredanne/apache-lucy,nwellnhof/lucy,nwellnhof/lucy,rectang/lucy,rectang/lucy,kidaa/lucy,pombredanne/apache-lucy,pombredanne/apache-lucy,apache/lucy,kidaa/lucy,apache/lucy,rectang/lucy,rbevers/lucy,nwellnhof/lucy,nwellnhof/lucy,apache/lucy,rectang/lucy