As keystoneclient and other services rely more on keystoneauth we should
assume that keystoneauth is our base auth library, not keystoneclient
and start to default to the objects provided from there. This will make
it easier to remove these objects when the time comes.

Use the AUTH_INTERFACE special object from keystoneauth in most places.
This uses it everywhere that is actually session independant. For
example it is not changed within the keystoneclient auth plugins
themselves as they are directly compatible with keystoneauth.

Change-Id: Ibc1224fca98c852106feb78c624b0b2f22b3a19d

As keystoneclient and other services rely more on keystoneauth we should
assume that keystoneauth is our base auth library, not keystoneclient
and start to default to the objects provided from there. This will make
it easier to remove these objects when the time comes.

The easiest thing to move is the keystoneclient fixtures in favor of the
keystoneauth fixtures.

Change-Id: I5a784795536cec6c7ca5eead3f13b1e7a6e45346

Deprecate auth plugins in favour of those from keystoneauth.

Change-Id: I8963ded9b68569717d7a6e30623ee78301b59a4a
Implements: bp deprecate-to-ksa

Deprecate the keystoneclient Session object in favour of keystoneauth's
Session.

Change-Id: I26e000d626a466f63d10d2a961adc698f8de0636
Implements: bp deprecate-to-ksa

Move all the existing tests to the unit/ subdirectory. This gives us
some room to add a functional/ directory later with other tests.

Change-Id: I0fb8d5b628eb8ee1f35f05f42d0c0ac9f285e8c3
Implements: functional-testing