Remove unnecessary setting from CredentialsTests

In CredentialsTests, ClosingHttp is not used.
And TempestConfigPrivate setting is duplicated between test classes.
This patch removes them for cleanup.

Change-Id: Ia909018c8e6a18c1e9e00f395a5447d881820269
diff --git a/tempest/tests/test_credentials.py b/tempest/tests/test_credentials.py
index ea576c4..fc80fe2 100644
--- a/tempest/tests/test_credentials.py
+++ b/tempest/tests/test_credentials.py
@@ -24,7 +24,6 @@
 from tempest import exceptions
 from tempest.tests import base
 from tempest.tests import fake_config
-from tempest.tests import fake_http
 from tempest.tests import fake_identity
 
 
@@ -39,8 +38,6 @@
 
     def setUp(self):
         super(CredentialsTests, self).setUp()
-        self.fake_http = fake_http.fake_httplib2(return_type=200)
-        self.stubs.Set(http.ClosingHttp, 'request', self.fake_http.request)
         self.useFixture(fake_config.ConfigFixture())
         self.stubs.Set(config, 'TempestConfigPrivate', fake_config.FakePrivate)
 
@@ -83,7 +80,6 @@
     def setUp(self):
         super(KeystoneV2CredentialsTests, self).setUp()
         self.stubs.Set(http.ClosingHttp, 'request', self.identity_response)
-        self.stubs.Set(config, 'TempestConfigPrivate', fake_config.FakePrivate)
 
     def _verify_credentials(self, credentials_class, filled=True,
                             creds_dict=None):