Add "parameter_defaults" to the environment

This give the user a way to set defaults recursively down nested stacks
without having to create the parameter in every template (it's ignored
if the template does not have the parameter).

blueprint env-nested-usability
Change-Id: Ie6b4481417204a527d322fd532c341b9acbce473
diff --git a/common/test.py b/common/test.py
index 43336a9..7478f64 100644
--- a/common/test.py
+++ b/common/test.py
@@ -17,6 +17,7 @@
 import re
 import six
 import subprocess
+import testscenarios
 import testtools
 import time
 
@@ -63,7 +64,8 @@
         return randbits
 
 
-class HeatIntegrationTest(testtools.TestCase):
+class HeatIntegrationTest(testscenarios.WithScenarios,
+                          testtools.TestCase):
 
     def setUp(self):
         super(HeatIntegrationTest, self).setUp()