Fix test_list_flavors for compute microversion 2.55

Description field is added to the response of list_flavors in
compute microversion 2.55, so we should add description to flavor_min_detail
when microversion is greater than 2.54.

Change-Id: I0f18994344f6a16f7e0942928093beda31dc9e0a

tempest/api/compute/flavors/test_flavors.py

@@ -27,6 +27,9 @@ class FlavorsV2TestJSON(base.BaseV2ComputeTest):
         flavor = self.flavors_client.show_flavor(self.flavor_ref)['flavor']
         flavor_min_detail = {'id': flavor['id'], 'links': flavor['links'],
                              'name': flavor['name']}
+        # description field is added to the response of list_flavors in 2.55
+        if not self.is_requested_microversion_compatible('2.54'):
+            flavor_min_detail.update({'description': flavor['description']})
         self.assertIn(flavor_min_detail, flavors)
 
     @decorators.idempotent_id('6e85fde4-b3cd-4137-ab72-ed5f418e8c24')