remove unused LOG

This is to remove unused LOG to keep code clean.

Change-Id: Ic544157b19cefb4120381f3314334c60a9020baf

Author: ji-xuepeng

openstackclient/api/auth_plugin.py

@@ -13,15 +13,11 @@
 
 """Authentication Plugin Library"""
 
-import logging
-
 from keystoneauth1 import loading
 from keystoneauth1 import token_endpoint
 
 from openstackclient.i18n import _
 
-LOG = logging.getLogger(__name__)
-
 
 class TokenEndpoint(loading.BaseLoader):
     """Auth plugin to handle traditional token/endpoint usage