Add explicit test_auth dependencies

[dbutenhof]

PBENCH-1130

Several tests in test_auth.py implicitly depended on previous DB init; they were failing occasionally in CI parallel test runs when scheduled without the prior setup.

Resolves #3381

[riya-17]

@dbutenhof why this db_session was not used earlier?

[dbutenhof]

@dbutenhof why this db_session was not used earlier?

I assume it was an oversight when the tests were written. Probably tested by running the entire test file, which succeeded because an earlier test (in normal sequential run order) had initialized the DB. Several of the tests use authentication tokens that end up pulling in the client fixture, which initializes the database (3 or 4 fixtures down).

The problem is that in the CI, we run tests in parallel, out of order; and sometimes, randomly, one of these tests gets run in a sequence without that setup. It's tricky.

[riya-17]

Thanks @dbutenhof