refactor test_catalog

- Tests for "missing" attributes are actually testing with null values,
  not missing keys.
- Not being able to explicitly provide alternative URLs resulting in
  hacky workarounds that can be avoiding by simply exposing kwargs with
  reasonable defaults
- Several tests redundantly asserted the expected response status, which
  is already handled by the test framework

Change-Id: Icadb4927bcf03ca7e79fef1507e419a4932f32a9
Related-Bug: 1250765
Formalize deprecation of token_api.list_tokens

The token_api.list_tokens method should really only be used internally
to keystone.  This has been the case (as per the docstring) since the
Havana development cycle.  This patchset formalizes the deprecation and
slates the public access to token_api.list_tokens to be removed once
Icehouse ships.

bp: deprecated-as-of-icehouse
Change-Id: I30a066d3775e67fd4a84f07dc351fcfd62751045
Merge "refactor test_catalog"
Merge "Formalize deprecation of token_api.list_tokens"