Support removal of last_activity session flag

This is a simple change that will support removal of the last activiy
session field within the horizon middleware.  Whith this change, a bunch
of horizon code can be removed.

Change-Id: Ia1c9f116ce731b80fb66a191d937a5ef509c81e9
Partialy-Closes: #1450914

openstack_auth/backend.py

@@ -13,7 +13,9 @@
 
 """ Module defining the Django auth backend class for the Keystone API. """
 
+import datetime
 import logging
+import pytz
 
 from django.conf import settings
 from django.utils.translation import ugettext_lazy as _
@@ -189,6 +191,11 @@ class KeystoneBackend(object):
         if request is not None:
             request.session['unscoped_token'] = unscoped_token
             request.user = user
+            timeout = getattr(settings, "SESSION_TIMEOUT", 3600)
+            token_life = user.token.expires - datetime.datetime.now(pytz.utc)
+            session_time = min(timeout, token_life.seconds)
+            request.session.set_expiry(session_time)
+
             scoped_client = keystone_client_class(session=session,
                                                   auth=scoped_auth)
 

openstack_auth/views.py

@@ -12,7 +12,6 @@
 # limitations under the License.
 import logging
 import re
-import time
 
 import django
 from django.conf import settings
@@ -124,7 +123,6 @@ def login(request, template_name=None, extra_context=None, **kwargs):
         region_name = regions.get(region)
         request.session['region_endpoint'] = region
         request.session['region_name'] = region_name
-        request.session['last_activity'] = int(time.time())
     return res