Enable testing of Swift with no auth system

Currently, all test cases in tempest cannot work without Keystone. However, with respect to Swift test, tempest should work without Keystone. There are three reasons:

1. Not just swift but any openstack component can be used as private cloud or as backend services of any other system. In these cases, authentication system is not mandatory. However, if someone want to use Tempest for testing such Swift cluster, he or she has to build Keystone for only testing purpose.

2. Actually, a lot of Swift clusters are built with tempauth or specific auth system rather than keystone because Swift can be used independently of other OpenStack components. Therefore, Swift tests in Tempest should be independent of Keystone.

3. Some responses of Swift API are subject to whether authentication system is built in or not. Such responses should be also tested in Tempest.