fix test_flavors_extra_specs failure

tempest.api.compute.admin.test_flavors_extra_specs.FlavorsExtraSpecsTestXML
failed due to test_flavor2 already exists

Fixing Bug 1220034

Change-Id: I259f4202978ac20d341349d1d227c6ef14c31d9b
diff --git a/tempest/api/compute/admin/test_flavors_extra_specs.py b/tempest/api/compute/admin/test_flavors_extra_specs.py
index 7b79a12..f2f82b5 100644
--- a/tempest/api/compute/admin/test_flavors_extra_specs.py
+++ b/tempest/api/compute/admin/test_flavors_extra_specs.py
@@ -58,6 +58,7 @@
     @classmethod
     def tearDownClass(cls):
         resp, body = cls.client.delete_flavor(cls.flavor['id'])
+        cls.client.wait_for_resource_deletion(cls.flavor['id'])
         super(FlavorsExtraSpecsTestJSON, cls).tearDownClass()
 
     @attr(type='gate')