Remove unnecessary usuage of instance variable

This is to change some instance variables to local variables,
and remove some unused instance variables.

Change-Id: Id2e7a1dcad4e51df488094ba9fb837410802828b
diff --git a/tempest/api/identity/admin/v3/test_trusts.py b/tempest/api/identity/admin/v3/test_trusts.py
index 7a569b7..ec64e0c 100644
--- a/tempest/api/identity/admin/v3/test_trusts.py
+++ b/tempest/api/identity/admin/v3/test_trusts.py
@@ -46,21 +46,21 @@
 
     def create_trustor_and_roles(self):
         # create a project that trusts will be granted on
-        self.trustor_project_name = data_utils.rand_name(name='project')
+        trustor_project_name = data_utils.rand_name(name='project')
         project = self.projects_client.create_project(
-            self.trustor_project_name, domain_id='default')['project']
+            trustor_project_name, domain_id='default')['project']
         self.trustor_project_id = project['id']
         self.assertIsNotNone(self.trustor_project_id)
 
         # Create a trustor User
-        self.trustor_username = data_utils.rand_name('user')
-        u_desc = self.trustor_username + 'description'
-        u_email = self.trustor_username + '@testmail.xx'
-        self.trustor_password = data_utils.rand_password()
+        trustor_username = data_utils.rand_name('user')
+        u_desc = trustor_username + 'description'
+        u_email = trustor_username + '@testmail.xx'
+        trustor_password = data_utils.rand_password()
         user = self.users_client.create_user(
-            name=self.trustor_username,
+            name=trustor_username,
             description=u_desc,
-            password=self.trustor_password,
+            password=trustor_password,
             email=u_email,
             project_id=self.trustor_project_id,
             domain_id='default')['user']
@@ -95,10 +95,10 @@
         # Initialize a new client with the trustor credentials
         creds = common_creds.get_credentials(
             identity_version='v3',
-            username=self.trustor_username,
-            password=self.trustor_password,
+            username=trustor_username,
+            password=trustor_password,
             user_domain_id='default',
-            tenant_name=self.trustor_project_name,
+            tenant_name=trustor_project_name,
             project_domain_id='default',
             domain_id='default')
         os = clients.Manager(credentials=creds)
diff --git a/tempest/api/identity/v3/test_users.py b/tempest/api/identity/v3/test_users.py
index f263258..e7998ee 100644
--- a/tempest/api/identity/v3/test_users.py
+++ b/tempest/api/identity/v3/test_users.py
@@ -34,8 +34,6 @@
         super(IdentityV3UsersTest, cls).resource_setup()
         cls.creds = cls.os.credentials
         cls.user_id = cls.creds.user_id
-        cls.username = cls.creds.username
-        cls.password = cls.creds.password
 
     def _update_password(self, original_password, password):
         self.non_admin_users_client.update_user_password(