(ensure-reduced x)
If x is already reduced?, returns it, else returns (reduced x)
(ensure-reduced :foo)
;;=> object[clojure.lang.Reduced 0x7dc19a70 {:status :ready, :val :foo}]
(ensure-reduced (reduced :foo))
;;=> object[clojure.lang.Reduced 0x45385f75 {:status :ready, :val :foo}]