Fix V3 credential behavior, documentation

Fixing V3 credential behavior so that contradicting parameter combinations
do not result in unpredictable behavior.  Updating accounts.yaml.sample
file to reference the correct location of the credentials
classes and to describe the updated behavior of Identity V3 attributes.

Change-Id: I29efe778afcb1e4a55dffd6a8ed8212d62a4dd15
diff --git a/tempest/tests/lib/test_auth.py b/tempest/tests/lib/test_auth.py
index ebcfe82..6a01490 100644
--- a/tempest/tests/lib/test_auth.py
+++ b/tempest/tests/lib/test_auth.py
@@ -530,3 +530,43 @@
 
         expected = 'http://fake_url/v3'
         self._test_base_url_helper(expected, filters, ('token', auth_data))
+
+
+class TestKeystoneV3Credentials(base.TestCase):
+    def testSetAttrUserDomain(self):
+        creds = auth.KeystoneV3Credentials()
+        creds.user_domain_name = 'user_domain'
+        creds.domain_name = 'domain'
+        self.assertEqual('user_domain', creds.user_domain_name)
+        creds = auth.KeystoneV3Credentials()
+        creds.domain_name = 'domain'
+        creds.user_domain_name = 'user_domain'
+        self.assertEqual('user_domain', creds.user_domain_name)
+
+    def testSetAttrProjectDomain(self):
+        creds = auth.KeystoneV3Credentials()
+        creds.project_domain_name = 'project_domain'
+        creds.domain_name = 'domain'
+        self.assertEqual('project_domain', creds.user_domain_name)
+        creds = auth.KeystoneV3Credentials()
+        creds.domain_name = 'domain'
+        creds.project_domain_name = 'project_domain'
+        self.assertEqual('project_domain', creds.project_domain_name)
+
+    def testProjectTenantNoCollision(self):
+        creds = auth.KeystoneV3Credentials(tenant_id='tenant')
+        self.assertEqual('tenant', creds.project_id)
+        creds = auth.KeystoneV3Credentials(project_id='project')
+        self.assertEqual('project', creds.tenant_id)
+        creds = auth.KeystoneV3Credentials(tenant_name='tenant')
+        self.assertEqual('tenant', creds.project_name)
+        creds = auth.KeystoneV3Credentials(project_name='project')
+        self.assertEqual('project', creds.tenant_name)
+
+    def testProjectTenantCollision(self):
+        attrs = {'tenant_id': 'tenant', 'project_id': 'project'}
+        self.assertRaises(
+            exceptions.InvalidCredentials, auth.KeystoneV3Credentials, **attrs)
+        attrs = {'tenant_name': 'tenant', 'project_name': 'project'}
+        self.assertRaises(
+            exceptions.InvalidCredentials, auth.KeystoneV3Credentials, **attrs)