Make test_subjob cross platform
Make test_subjob cross platform

There were hard coded environment variable setter commands in the tests that fail on Windows.
This commit uses the get_environment_variable_setter_command instead.

box/ClusterRunner,box/ClusterRunner,Medium/ClusterRunner,josephharrington/ClusterRunner,nickzuber/ClusterRunner,josephharrington/ClusterRunner,Medium/ClusterRunner,nickzuber/ClusterRunner