Fix tests for Octavia API compat changes

Change-Id: I524c5a3534914e6c130dd4c5bed2be77d7e38c74
Depends-On: https://review.openstack.org/#/c/563341/
diff --git a/octavia_tempest_plugin/tests/waiters.py b/octavia_tempest_plugin/tests/waiters.py
index 7825782..44138a4 100644
--- a/octavia_tempest_plugin/tests/waiters.py
+++ b/octavia_tempest_plugin/tests/waiters.py
@@ -49,7 +49,14 @@
     LOG.info('Waiting for {name} status to update to {status}'.format(
         name=show_client.__name__, status=status))
     while True:
-        response = show_client(id)
+        if status == const.DELETED:
+            try:
+                response = show_client(id)
+            except exceptions.NotFound:
+                return
+        else:
+            response = show_client(id)
+
         if root_tag:
             object_details = response[root_tag]
         else: