Changes

global_platform: ensure ArgumentParser gets a list for choices

When we use the argument parser with choices, we sometimes use a
list that we derive from a dictionary. However if we do that we
still must ensure that we really put a list and not a dict_values
or dict_keys class as parameter because this won't work any longer
with cmd2 version 2.5.0

Related: OS#6601
Change-Id: I165fefd8feb0d96cedc15d036fb32da381f711b3