List amphora: use test's loadbalancer

Test `test_amphora_list_and_show` gets amphoras of loadbalancer
created in resource setup, but it could be not ready and amphorae
fileds aren't filled out.

Related-PRODX: PRODX-17934
Change-Id: I58fc8add761279af1307bb5b0e964697d79ab36a
diff --git a/octavia_tempest_plugin/tests/api/v2/test_amphora.py b/octavia_tempest_plugin/tests/api/v2/test_amphora.py
index 91241c6..76662bb 100644
--- a/octavia_tempest_plugin/tests/api/v2/test_amphora.py
+++ b/octavia_tempest_plugin/tests/api/v2/test_amphora.py
@@ -108,9 +108,9 @@
         # Test filtering by loadbalancer_id
         amphorae = self.lb_admin_amphora_client.list_amphorae(
             query_params='{loadbalancer_id}={lb_id}'.format(
-                loadbalancer_id=const.LOADBALANCER_ID, lb_id=self.lb_id))
+                loadbalancer_id=const.LOADBALANCER_ID, lb_id=lb_id))
         self.assertEqual(self._expected_amp_count(amphorae), len(amphorae))
-        self.assertEqual(self.lb_id, amphorae[0][const.LOADBALANCER_ID])
+        self.assertEqual(lb_id, amphorae[0][const.LOADBALANCER_ID])
 
         # Test that a different user, with load balancer member role, cannot
         # see this amphora