Add assertion after domain deletion

This commit adds an assertion to verify the domain is not found in
the list after deletion.

Change-Id: I41fe7f0192632c1700082c72c1db4490aef1a47d
Closes-Bug: 1512597
diff --git a/tempest/api/identity/admin/v3/test_domains.py b/tempest/api/identity/admin/v3/test_domains.py
index 742d737..15bea28 100644
--- a/tempest/api/identity/admin/v3/test_domains.py
+++ b/tempest/api/identity/admin/v3/test_domains.py
@@ -28,6 +28,11 @@
         # or else it would result in unauthorized error
         self.client.update_domain(domain_id, enabled=False)
         self.client.delete_domain(domain_id)
+        # Asserting that the domain is not found in the list
+        # after deletion
+        body = self.client.list_domains()['domains']
+        domains_list = [d['id'] for d in body]
+        self.assertNotIn(domain_id, domains_list)
 
     @test.idempotent_id('8cf516ef-2114-48f1-907b-d32726c734d4')
     def test_list_domains(self):