[test] Fix broken rllib test (#2446)
[test] Fix broken rllib test (#2446)

This fixes the broken build.
richardliaw/ray,richardliaw/ray,stephanie-wang/ray,atumanov/ray,robertnishihara/ray,pcmoritz/ray-1,ujvl/ray-ng,robertnishihara/ray,pcmoritz/ray-1,ujvl/ray-ng,atumanov/ray,ray-project/ray,ujvl/ray-ng,atumanov/ray,richardliaw/ray,atumanov/ray,stephanie-wang/ray,ray-project/ray,robertnishihara/ray,pcmoritz/ray-1,robertnishihara/ray,ray-project/ray,atumanov/ray,ray-project/ray,ray-project/ray,ujvl/ray-ng,atumanov/ray,richardliaw/ray,richardliaw/ray,ray-project/ray,stephanie-wang/ray,stephanie-wang/ray,stephanie-wang/ray,pcmoritz/ray-1,robertnishihara/ray,pcmoritz/ray-1,richardliaw/ray,richardliaw/ray,robertnishihara/ray,stephanie-wang/ray,atumanov/ray,atumanov/ray,robertnishihara/ray,richardliaw/ray,pcmoritz/ray-1,stephanie-wang/ray,robertnishihara/ray,pcmoritz/ray-1,robertnishihara/ray,stephanie-wang/ray,pcmoritz/ray-1,stephanie-wang/ray,ray-project/ray,ray-project/ray