Remove HTTP_SUCCESS from tempest.test module

We don't need HTTP_SUCCESS values in Tempest because it isn't used
anywhere.

Change-Id: I8004d4844588fe84ca74f674f54d73768796d92d
diff --git a/tempest/test.py b/tempest/test.py
index cc8370c..281f0f2 100644
--- a/tempest/test.py
+++ b/tempest/test.py
@@ -39,9 +39,6 @@
 
 CONF = config.CONF
 
-# All the successful HTTP status codes from RFC 2616
-HTTP_SUCCESS = (200, 201, 202, 203, 204, 205, 206)
-
 
 def attr(*args, **kwargs):
     """A decorator which applies the  testtools attr decorator