Re-enable internal DNS tests

Re-enable internal DNS tests as assocaited Neutron
changes have now landed.

Assert that 'starwars' has not been configured in
the search path for the test instance.

Related-Bug: 1826419
Change-Id: I9d16f3b2dacd1e753c8f9d803c889c537a3f3378
diff --git a/neutron_tempest_plugin/scenario/test_internal_dns.py b/neutron_tempest_plugin/scenario/test_internal_dns.py
index dfd42b0..13ca797 100644
--- a/neutron_tempest_plugin/scenario/test_internal_dns.py
+++ b/neutron_tempest_plugin/scenario/test_internal_dns.py
@@ -35,7 +35,6 @@
           2.1) ping the other VM's internal IP
           2.2) ping the other VM's hostname
         """
-        self.skipTest('Disable whilst associated changes land into Neutron')
         network = self.create_network(dns_domain='starwars.')
         self.setup_network_and_server(network=network, server_name='luke')
         self.create_pingable_secgroup_rule(
@@ -71,10 +70,10 @@
         self.check_remote_connectivity(
             ssh_client, leia_port['fixed_ips'][0]['ip_address'],
             timeout=CONF.validation.ping_timeout * 10)
-        self.assertIn(
-            'openstackgate.local',
-            ssh_client.exec_command('cat /etc/resolv.conf')
-        )
+
+        resolv_conf = ssh_client.exec_command('cat /etc/resolv.conf')
+        self.assertIn('openstackgate.local', resolv_conf)
+        self.assertNotIn('starwars', resolv_conf)
 
         self.check_remote_connectivity(ssh_client, 'leia')
         self.check_remote_connectivity(ssh_client, 'leia.openstackgate.local')