Correct docstring for assertResponseSuccessful

The example had a parameter that didn't exist for the method.

Change-Id: I17a63326e109776dd3192cfb8af5ca85f49a8e5f
update example with a status code we actually use

Keystone doesn't return HTTP 203 today, so the example is a bit
misleading. HTTP 204 is something we use on assignment operations, for
example.

Change-Id: I874c02ae44f4d49848c49451c40005c7f1e33865
Add schema check for OS-FEDERATION mapping table

Implement 'mapping' schema check ensuring the table was correctly
created in the database.

Change-Id: Ic69864bb4327657dc1b981de4229abce9e86aa86