When an attribute is known-fulltext, don't hit AllDatoms. (#576) r=nalexander
When an attribute is known-fulltext, don't hit AllDatoms. (#576) r=nalexander


ncalexan/mentat,ncalexan/mentat,mozilla/mentat,mozilla/mentat,ncalexan/datomish,mozilla/mentat,ncalexan/mentat,ncalexan/mentat,ncalexan/datomish,mozilla/mentat,mozilla/mentat,mozilla/mentat,ncalexan/mentat,ncalexan/mentat