functional: Handle ovsdb monitor returning inserts in different checks

The test case should be satisfied as long as monitor receives the
events; it doesn't matter if the insert events were received at the same
call to process_events.

Closes-Bug: #2095034
Change-Id: Ib5b78c3bdb9f4efbbc9bad9a45be45fb97da3c1d

neutron/tests/functional/agent/common/test_ovsdb_monitor.py

@@ -65,10 +65,20 @@ class SimpleInterfaceMonitorTestCase(base.BaseSudoTestCase):
         p2 = self.useFixture(net_helpers.OVSPortFixture(br_2))
 
         ports_expected = {p1.port.name, p2.port.name}
+
+        def process_new_events(mon, ports_expected):
+            remaining = self._check_port_events(
+                mon, ports_expected=ports_expected)
+
+            # Next time check only the ports not seen yet
+            ports_expected.clear()  # Python doesn't support {:} syntax
+            ports_expected.update(remaining)
+
+            return bool(ports_expected)  # True if there are remaining ports
+
         try:
             common_utils.wait_until_true(
-                lambda: not self._check_port_events(
-                    mon_no_filter, ports_expected=ports_expected),
+                lambda: not process_new_events(mon_no_filter, ports_expected),
                 timeout=5)
         except common_utils.WaitTimeout:
             self.fail('Interface monitor not filtered did not received an '