orchestration add basic support for environment API test

Adds support for passing environment into create/update API calls,
and implements a basic test which proves a parameter can be passed
via an environment.

These links document this interface, which is currently not tested
in tempest:
http://api.openstack.org/api-ref-orchestration-v1.html
http://docs.openstack.org/developer/heat/template_guide/environment.html

Change-Id: Id3e3a69370603d5a700ef0d0b1dcb09a3765b09f
Partial-Bug: #1317095
diff --git a/tempest/api/orchestration/base.py b/tempest/api/orchestration/base.py
index 4e40de9..df3efdb 100644
--- a/tempest/api/orchestration/base.py
+++ b/tempest/api/orchestration/base.py
@@ -60,11 +60,13 @@
         return admin_client
 
     @classmethod
-    def create_stack(cls, stack_name, template_data, parameters={}):
+    def create_stack(cls, stack_name, template_data, parameters={},
+                     environment=None):
         resp, body = cls.client.create_stack(
             stack_name,
             template=template_data,
-            parameters=parameters)
+            parameters=parameters,
+            environment=environment)
         stack_id = resp['location'].split('/')[-1]
         stack_identifier = '%s/%s' % (stack_name, stack_id)
         cls.stacks.append(stack_identifier)