Update test.py

[mhdmyz]

I highly suggest for simplifying and easier debugging and better readability and understandability of the codes, the environment creation gets it's own function and gets separated from the train and test functions. One of the prominent advantages of FinRL-Meta is it's modularity and having different independent layers, which the proposed change helps going further in this direction.

[YangletLiu]

@mhdmyz thanks very much! We will do a code review soon!