Mark "test_subport_connectivity_soft_reboot" as unstable

This issue is related to:
* https://bugs.launchpad.net/neutron/+bug/2033887: the patches
  previously merged in the Neutron repository [1][2] should be
  reverted.
* https://bugs.launchpad.net/neutron/+bug/2024160: this issue
  is still present.

[1]https://review.opendev.org/c/openstack/neutron/+/882581
[2]https://review.opendev.org/c/openstack/neutron/+/888776

Change-Id: I9d8d76810d15913c29610464ab1b8fa34863aaf6
Related-Bug: #2024160
Related-Bug: #2033887
diff --git a/neutron_tempest_plugin/scenario/test_trunk.py b/neutron_tempest_plugin/scenario/test_trunk.py
index b994775..2ba8f13 100644
--- a/neutron_tempest_plugin/scenario/test_trunk.py
+++ b/neutron_tempest_plugin/scenario/test_trunk.py
@@ -277,6 +277,7 @@
             self._wait_for_trunk(vm.trunk)
             self._assert_has_ssh_connectivity(vm1.ssh_client)
 
+    @test.unstable_test("bug 2033887 / bug 2024160")
     @testtools.skipUnless(
         (CONF.neutron_plugin_options.advanced_image_ref or
          CONF.neutron_plugin_options.default_image_is_advanced),