Update reconfig event ltime on (smart) reconfig

Make sure to update the last reconfig event ltime in the layout state
during a (smart) reconfig. This is important in order to unblock
pipelines when a tenant reconfig event is lost.

So far the last reconfig event ltime was passed as -1, but wasn't set in
the layout state since the ltime is not allowed to go backward.

Change-Id: Iab04a962abbfbe901c22e4d5f1d484e3f53b0d33

tests/unit/test_scheduler.py

@@ -3960,6 +3960,10 @@ class TestScheduler(ZuulTestCase):
             else:
                 time.sleep(0)
 
+        self.assertGreater(new.last_reconfigured, old.last_reconfigured)
+        self.assertGreater(new.last_reconfigure_event_ltime,
+                           old.last_reconfigure_event_ltime)
+
     def test_tenant_reconfiguration_command_socket(self):
         "Test that single-tenant reconfiguration via command socket works"
 

zuul/scheduler.py

@@ -1528,7 +1528,7 @@ class Scheduler(threading.Thread):
                     with self.createZKContext(lock, self.log) as ctx:
                         if tenant is not None:
                             self._reconfigureTenant(ctx, min_ltimes,
-                                                    -1,
+                                                    event.zuul_event_ltime,
                                                     tenant, old_tenant)
                         else:
                             self._reconfigureDeleteTenant(ctx, old_tenant)