Call save/restorePosition on all child stages of MultiPlanStage and CachedPlanStage
SERVER-3304 Clean up index between inserting a Timestamp and a Date

This should be unnecessary once SERVER-3304 is resolved.
SERVER-13635 Make dbtest take --storageEngine
SERVER-13635 Move mmapv1 specific dbtests to mmaptest and skip if using other engine
Don't leak query trees in distinct dbtest
SERVER-13951 Clean up WUOWs in a few dbtests