Fix import order to comply with import ordering rules.

Fixes pep8 failures TEMPEST N306 and N301.

Change-Id: I87d6ef4058170da73ff64d4e4a4caf43f8a18046
diff --git a/tempest/tests/identity/admin/test_tenants.py b/tempest/tests/identity/admin/test_tenants.py
index 1b4ec18..226aae6 100644
--- a/tempest/tests/identity/admin/test_tenants.py
+++ b/tempest/tests/identity/admin/test_tenants.py
@@ -17,8 +17,8 @@
 
 import unittest2 as unittest
 
-from tempest import exceptions
 from tempest.common.utils.data_utils import rand_name
+from tempest import exceptions
 from tempest.tests.identity import base