Use Python 2.6.x compatible syntax for dict comprehension

The dict comprehension syntax used here was added in 2.7.
With minimal change it can be adjusted for Python 2.6.x

Change-Id: I920c4a4181fdf5c696ba873224a2c07f09e914e4
diff --git a/tempest/tests/test_rest_client.py b/tempest/tests/test_rest_client.py
index ba43daf..9f07972 100644
--- a/tempest/tests/test_rest_client.py
+++ b/tempest/tests/test_rest_client.py
@@ -164,7 +164,7 @@
 
     keys = ["fake_key1", "fake_key2"]
     values = ["fake_value1", "fake_value2"]
-    item_expected = {key: value for key, value in zip(keys, values)}
+    item_expected = dict((key, value) for (key, value) in zip(keys, values))
     list_expected = {"body_list": [
         {keys[0]: values[0]},
         {keys[1]: values[1]},