Our base class for API tests has a helper that can log in the test

client, giving a couple knobs for whether the user should be an admin or

part of a local host. We really ought to be using this more broadly (as

opposed to just manually hardcoding usernames from our user fixtures),

so I've relocated it to the base test case, renamed it to be

not-private, and included a fallback for any third-party code that might

use the old name. All of our references have been updated.

Ran unit tests.