Update paver bok_choy (test) commands to reflect new default vars.

@clytwynec @nasthagiri 

This takes into account recent changes for how bok-choy commands are composed in paver. (Should also bring Jenkins back to green.)


Yeah..ok this is because the bok_choy statement is now wrapped by the logic starting here: https://github.com/edx/edx-platform/blob/dedd88ccf40ec0986265aef131bec018cff952d0/pavelib/bok_choy.py#L89

The unit test was written according to the bokchoytestsuite object, and it looks like this logic is happening outside of that context (i.e. after the object has been created, it gets updated).