Remove hard-coded tests against 'phabricator' namespace in setup

Summary: See https://github.com/facebook/arcanist/issues/49

Test Plan:

• Turned on setup mode with non-default namespace.
• Verified that setup tests passed.

Reviewers: btrahan, vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D3274