Mark trunk tests as unstable

Currently failing rate is about 40% of the scenario tests in dvr
multinode flavor. Let's skip the trunk tests as they might be the last
one failing while in parallel attempting to troubleshoot the issue and
working on the fix.

Change-Id: I29f1dc56273a71789474596ffee1688d3443d3bc
Related-bug: #1766701

neutron_tempest_plugin/scenario/test_trunk.py

@@ -140,6 +140,7 @@ def _wait_for_server(self, server):
                                 CONF.validation.image_ssh_user,
                                 self.keypair['private_key'])
 
+    @utils.unstable_test("bug 1766701")
     @decorators.idempotent_id('bb13fe28-f152-4000-8131-37890a40c79e')
     def test_trunk_subport_lifecycle(self):
         """Test trunk creation and subport transition to ACTIVE status.
@@ -220,6 +221,7 @@ def test_trunk_subport_lifecycle(self):
                                 CONF.validation.image_ssh_user,
                                 self.keypair['private_key'])
 
+    @utils.unstable_test('bug 1766701')
     @testtools.skipUnless(
           CONF.neutron_plugin_options.image_is_advanced,
           "Advanced image is required to run this test.")