Remove unused LOG from clients.py

LOG is not used in clients.py, so this is to remove
it for code clean.

Change-Id: I517bb46e0d47c59678266a8912c535ec68edf5e9
diff --git a/tempest/clients.py b/tempest/clients.py
index 467ef9c..93323bd 100644
--- a/tempest/clients.py
+++ b/tempest/clients.py
@@ -13,8 +13,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from oslo_log import log as logging
-
 from tempest import config
 from tempest.lib import auth
 from tempest.lib import exceptions as lib_exc
@@ -23,7 +21,6 @@
 from tempest.services import orchestration
 
 CONF = config.CONF
-LOG = logging.getLogger(__name__)
 
 
 class Manager(clients.ServiceClients):