Incorrect number of environments created when not using VecNormalize

[hai-h-nguyen]

When I do not use VecNormalize by commenting envs = VecNormalize(envs, gamma=gamma) inside envs.py, the number of environments created is incorrect, i.e. _thunk is called 7 times with n-processes=10, but only one environment is created since the env.seed function is called only once.