Make some test_list_projects tests work w/ pre-prov

This is part 2 of 2 commits to not force dynamic creds to execute
the following tests:
  * test_list_projects
  * test_list_projects_with_name
  * test_list_projects_with_domains
so that users with a cloud using the pre-provisioned credential
provider can execute these tests.
Part 1 did some refactoring[1]

The other tests cannot be moved because they require resources to
be created explained below:
  * test_list_projects_with_parent
    - if this test requires a project with a parent then we cannot
      use pre-provisioned credentials because there is no way to
      provide an account with a parent using the current
      implementation of the pre-provisioned credential provider.
  * test_list_projects_with_enabled
    - if this test requires projects that are disabled then we
      cannot use pre-provisioned credentials because there is no
      way to provide an account that is disabled with the current
      implementation of the pre-provisioned credential provider.

[1] https://review.openstack.org/#/c/583385/
Change-Id: I9ee67c8c99a33fa75fb7faa1efcccd5bba5b05ef
1 file changed