Support running func tests against non-<account>:<user> auth systems

Our func tests are a little split-brain about whether to support an auth system that doesn't have user ids like <account>:<user>. In setup_package [1] we seem to tolerate it, and a bunch of tests work with such a system, but then a bunch of others (half, give or take?) bomb out with KeyErrors because their test env looks for (say) tf.config['account2'] [2] [3] [4] [5].

I *think* this is just a matter of adding some

 if 'account2' in tf.config:
     ...

blocks in the appropriate places?

[1] https://github.com/openstack/swift/blob/2.9.0/test/functional/__init__.py#L661
[2] https://github.com/openstack/swift/blob/2.9.0/test/functional/tests.py#L1141
[3] https://github.com/openstack/swift/blob/2.9.0/test/functional/tests.py#L2732
[4] https://github.com/openstack/swift/blob/2.9.0/test/functional/tests.py#L3594
[5] https://github.com/openstack/swift/blob/2.9.0/test/functional/tests.py#L4442