Move fake get_credentials methods to test_auth

fake_auth_provider needed fake_credentials which needs auth module which
needs keystone service clients for implementing fake get_credentials and
get_default_credentials. So this dependency blocked moving rest_client
module to tempest-lib because test_rest_client needs fake_auth_provider
like:

  rest_client
     -> test_rest_client
        -> fake_auth_provider
           -> fake_credentials
              -> auth
                 -> identity_client of v2 and v3
                    -> rest_client

So a dependency loop existed.
Both get_credentials and get_default_credentials of fake_auth_provider
were used in test_auth only.
So this patch moves fake get_credentials methods to test_auth for breaking
the dependency loop.

Change-Id: Id12341de52204e2c428e10b4b758b700b0fbab09
diff --git a/tempest/tests/fake_auth_provider.py b/tempest/tests/fake_auth_provider.py
index 44c331e..bc68d26 100644
--- a/tempest/tests/fake_auth_provider.py
+++ b/tempest/tests/fake_auth_provider.py
@@ -13,16 +13,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from tempest.tests import fake_credentials
-
-
-def get_default_credentials(credential_type, fill_in=True):
-    return fake_credentials.FakeCredentials()
-
-
-def get_credentials(credential_type=None, fill_in=True, **kwargs):
-    return fake_credentials.FakeCredentials()
-
 
 class FakeAuthProvider(object):
 
diff --git a/tempest/tests/test_auth.py b/tempest/tests/test_auth.py
index fc05198..a191781 100644
--- a/tempest/tests/test_auth.py
+++ b/tempest/tests/test_auth.py
@@ -24,13 +24,20 @@
 from tempest.services.identity.json import identity_client as v2_client
 from tempest.services.identity.v3.json import identity_client as v3_client
 from tempest.tests import base
-from tempest.tests import fake_auth_provider
 from tempest.tests import fake_config
 from tempest.tests import fake_credentials
 from tempest.tests import fake_http
 from tempest.tests import fake_identity
 
 
+def fake_get_default_credentials(credential_type, fill_in=True):
+    return fake_credentials.FakeCredentials()
+
+
+def fake_get_credentials(credential_type=None, fill_in=True, **kwargs):
+    return fake_credentials.FakeCredentials()
+
+
 class BaseAuthTestsSetUp(base.TestCase):
     _auth_provider_class = None
     credentials = fake_credentials.FakeCredentials()
@@ -46,10 +53,9 @@
         self.useFixture(fake_config.ConfigFixture())
         self.stubs.Set(config, 'TempestConfigPrivate', fake_config.FakePrivate)
         self.fake_http = fake_http.fake_httplib2(return_type=200)
-        self.stubs.Set(auth, 'get_credentials',
-                       fake_auth_provider.get_credentials)
+        self.stubs.Set(auth, 'get_credentials', fake_get_credentials)
         self.stubs.Set(auth, 'get_default_credentials',
-                       fake_auth_provider.get_default_credentials)
+                       fake_get_default_credentials)
         self.auth_provider = self._auth(self.credentials)