fix mujoco_py installation in tensorflow-openai-ros image

[jacknlliu]

skip the license key installation when installing. Because we don't need mujoco at present.

We can't install mujoco_py because of the mujoco from DockerHub, but we can add installation for local build.

• add mujoco_py installation for local
• add gym and baselines installation with mujoco_py
• add roboschool installation with mujoco_py
• add rllab installation with mujoco_py

[jacknlliu]

NOTE: our long-term expectation is replacing mujoco by the open source physics engine dart.