Don't let replica restore initialize key when DCS was wiped (#2970)

It was happening from the branch where Patroni was supposed to be complain about converting standalone PG cluster to be governed by Patroni and exit.

patroni/ha.py

@@ -1849,10 +1849,9 @@ class Ha(object):
                             logger.fatal('system ID mismatch, node %s belongs to a different cluster: %s != %s',
                                          self.state_handler.name, self.cluster.initialize, data_sysid)
                             sys.exit(1)
-                elif self.cluster.is_unlocked() and not self.is_paused():
+                elif self.cluster.is_unlocked() and not self.is_paused() and not self.state_handler.cb_called:
                     # "bootstrap", but data directory is not empty
-                    if not self.state_handler.cb_called and self.state_handler.is_running() \
-                            and not self.state_handler.is_primary():
+                    if self.state_handler.is_running() and not self.state_handler.is_primary():
                         self._join_aborted = True
                         logger.error('No initialize key in DCS and PostgreSQL is running as replica, aborting start')
                         logger.error('Please first start Patroni on the node running as primary')

tests/test_ha.py

@@ -1585,6 +1585,11 @@ class TestHa(PostgresInit):
         self.p.is_primary = false
         self.ha.run_cycle()
         exit_mock.assert_called_once_with(1)
+        self.p.set_role('replica')
+        self.ha.dcs.initialize = Mock()
+        with patch.object(Postgresql, 'cb_called', PropertyMock(return_value=True)):
+            self.assertEqual(self.ha.run_cycle(), 'promoted self to leader by acquiring session lock')
+        self.ha.dcs.initialize.assert_not_called()
 
     @patch.object(Cluster, 'is_unlocked', Mock(return_value=False))
     def test_after_pause(self):