Fix Cumulative reward reset

unity-environment/Assets/ML-Agents/Scripts/Agent.cs

     public void Reset()
     {
         memory = new float[brain.brainParameters.memorySize];
-        CumulativeReward = 0f;
         stepCounter = 0;
         AgentReset();
     }
     public void ResetReward()
     {
         reward = 0;
+        CumulativeReward = 0f;
     }
 
 }