Fixed Bug#943092

Declared a varible 'release' to use te value in tempest.conf

Change-Id: Ib4f70bbcf52193af583ba7f082f73d495cdddb20
diff --git a/tempest/tests/test_servers_negative.py b/tempest/tests/test_servers_negative.py
index 70330d2..b038b61 100644
--- a/tempest/tests/test_servers_negative.py
+++ b/tempest/tests/test_servers_negative.py
@@ -2,9 +2,12 @@
 from tempest import openstack
 from tempest.common.utils.data_utils import rand_name
 from tempest import exceptions
+import tempest.config
 
 
 class ServersNegativeTest(unittest.TestCase):
+    release = tempest.config.TempestConfig().\
+            env.release_name
 
     @classmethod
     def setUpClass(cls):