Added code for issue #2036

Made necessary changes to ```humanoid_deep_mimic_env.py``` file, setting ```initial_frame``` to new position after simulation steps and setting ```SimTime``` using this new initial frame time

examples/pybullet/gym/pybullet_envs/deep_mimic/humanoid_deepmimic_gym_env.py

@@ -150,6 +150,8 @@ class HumanoidDeepMimicGymEnv(gym.Env):
     for s in range (8):
       #print("step:",s)
       self._pybullet_client.stepSimulation()
+    self._initial_frame = self._initial_frame + self._control_time_step
+    self._humanoid.setSimTime(self._initial_frame)
     reward = self._reward()
     done = self._termination()
     self._env_step_counter += 1