Fix Upstream test cases to be case insensitive

In any domain, due to case sensitivity, if a username
for the project and the username in tempest.conf or
accounts.yaml are not identical, then the test cases
are failing.

So, added .lower() method to change the username strings
to be case insensitive.

Closes-Bug: #1836618

Change-Id: Id7d079c881bbfae972d65ef6049f78da7f25fc1d
diff --git a/tempest/api/identity/v3/test_tokens.py b/tempest/api/identity/v3/test_tokens.py
index f13aa10..fa1c47f 100644
--- a/tempest/api/identity/v3/test_tokens.py
+++ b/tempest/api/identity/v3/test_tokens.py
@@ -43,7 +43,15 @@
         self.assertEqual(authenticated_token, token_body)
         # test to see if token has been properly authenticated
         self.assertEqual(authenticated_token['user']['id'], user_id)
-        self.assertEqual(authenticated_token['user']['name'], username)
+        # NOTE: resource name that are case-sensitive in keystone
+        # depends on backends such as MySQL or LDAP which are
+        # case-insensitive, case-preserving. Resource name is
+        # returned as it is stored in the backend, not as it is
+        # requested. Verifying the username with both lower-case to
+        # avoid failure on different backends
+        self.assertEqual(
+            authenticated_token['user']['name'].lower(), username.lower())
+
         self.non_admin_client.delete_token(subject_token)
         self.assertRaises(
             lib_exc.NotFound, self.non_admin_client.show_token, subject_token)
@@ -84,10 +92,17 @@
             self.assertIsNotNone(subject_id, 'Expected user ID in token.')
 
         subject_name = resp['user']['name']
+
         if username:
-            self.assertEqual(subject_name, username)
+            # NOTE: resource name that are case-sensitive in keystone
+            # depends on backends such as MySQL or LDAP which are
+            # case-insensitive, case-preserving. Resource name is
+            # returned as it is stored in the backend, not as it is
+            # requested. Verifying the username with both lower-case to
+            # avoid failure on different backends
+            self.assertEqual(subject_name.lower(), username.lower())
         else:
-            # Expect a user name, but don't know what it will be.
+            # Expect a user name, but don't know what it will be
             self.assertIsNotNone(subject_name, 'Expected user name in token.')
 
         self.assertEqual(resp['methods'][0], 'password')
@@ -110,7 +125,15 @@
             subject_token)['token']
         self.assertEqual(resp['x-subject-token'], subject_token)
         self.assertEqual(token_details['user']['id'], user.user_id)
-        self.assertEqual(token_details['user']['name'], user.username)
+        # NOTE: resource name that are case-sensitive in keystone
+        # depends on backends such as MySQL or LDAP which are
+        # case-insensitive, case-preserving. Resource name is
+        # returned as it is stored in the backend, not as it is
+        # requested. Verifying the username with both lower-case to
+        # avoid failure on different backends
+        self.assertEqual(
+            token_details['user']['name'].lower(),
+            user.username.lower())
         # Perform Delete Token
         self.non_admin_client.delete_token(subject_token)
         self.assertRaises(lib_exc.NotFound,