Improve test_amphora_failover

Add waiter for status ALLOCATED for new Amphora instance

Related-Prod: PRODX-22887
Change-Id: I45965e652ae00aa10e06dc3739407fb77debc322
diff --git a/octavia_tempest_plugin/tests/api/v2/test_amphora.py b/octavia_tempest_plugin/tests/api/v2/test_amphora.py
index 180e4f3..6d73bf0 100644
--- a/octavia_tempest_plugin/tests/api/v2/test_amphora.py
+++ b/octavia_tempest_plugin/tests/api/v2/test_amphora.py
@@ -239,6 +239,11 @@
 
         for new_amp in after_amphorae:
             self.assertNotEqual(amphora_1[const.ID], new_amp[const.ID])
+            waiters.wait_for_status(self.lb_admin_amphora_client.show_amphora,
+                                    new_amp[const.ID], const.STATUS,
+                                    const.STATUS_ALLOCATED,
+                                    CONF.load_balancer.build_interval,
+                                    CONF.load_balancer.build_timeout)
 
     @testtools.skipIf(CONF.load_balancer.test_with_noop,
                       'Log offload tests will not work in noop mode.')