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.)


Can we pass it **opts in the test? (Here: https://github.com/edx/edx-platform/blob/master/pavelib/paver_tests/test_paver_bok_choy_cmds.py#L12)