Get heat.tests.test_stack* working in py34 env

There are three tests skipped which needs further
addressing later on. However, fixing test_stack should prevent
future regressions for when a stack object is created.

partial blueprint heat-python34-support

Change-Id: I15bfd0990ebe248436c1a0c5e3f4f9a8332c2a57

heat/db/sqlalchemy/api.py

@@ -621,7 +621,14 @@ def user_creds_create(context):
         user_creds_ref.password = password
         user_creds_ref.decrypt_method = method
     user_creds_ref.save(_session(context))
-    return user_creds_ref
+    result = dict(user_creds_ref)
+
+    if values.get('trust_id'):
+        result['trust_id'] = values.get('trust_id')
+    else:
+        result['password'] = values.get('password')
+
+    return result
 
 
 def user_creds_get(user_creds_id):