Fix trunk test_subport_delete functional test

This change fixes a race condition between deleting a subport in the
trunk plugin and the actual deletion in the OVN NBDB.

Change-Id: I836d47a1879d474c2171905416a2838cfe3bab5a
Closes-Bug: #2067400

neutron/tests/functional/services/trunk/drivers/ovn/test_trunk_driver.py

@@ -19,12 +19,22 @@ from neutron_lib.objects import registry as obj_reg
 from neutron_lib.plugins import utils
 from neutron_lib.services.trunk import constants as trunk_consts
 from oslo_utils import uuidutils
+from ovsdbapp.backend.ovs_idl import event
 
 from neutron.common.ovn import constants as ovn_const
 from neutron.services.trunk import plugin as trunk_plugin
 from neutron.tests.functional import base
 
 
+class WaitForLogicalSwitchPortUpdateEvent(event.WaitEvent):
+    event_name = 'WaitForDataPathBindingCreateEvent'
+
+    def __init__(self):
+        table = 'Logical_Switch_Port'
+        events = (self.ROW_UPDATE,)
+        super().__init__(events, table, None, timeout=15)
+
+
 class TestOVNTrunkDriver(base.TestOVNFunctionalBase):
 
     def setUp(self):
@@ -117,10 +127,14 @@ class TestOVNTrunkDriver(base.TestOVNFunctionalBase):
     def test_subport_delete(self):
         with self.subport() as subport:
             with self.trunk([subport]) as trunk:
+                lsp_event = WaitForLogicalSwitchPortUpdateEvent()
+                self.mech_driver.nb_ovn.idl.notify_handler.watch_events(
+                    (lsp_event,))
                 self.trunk_plugin.remove_subports(self.context, trunk['id'],
                                                   {'sub_ports': [subport]})
                 new_trunk = self.trunk_plugin.get_trunk(self.context,
                                                         trunk['id'])
+                self.assertTrue(lsp_event.wait())
                 self._verify_trunk_info(new_trunk, has_items=False)
 
     def test_trunk_delete(self):