Fix traceback running instance-usage-audit

There were two errors here:
    1 was a missed joinload that was causing an error pulling info_cache.
    2 the exception listed in the bug, which was caused by tring to load data for a deleted instance.

This fixes bug 934539

Change-Id: Ifffb6a35c1f7bf8caa6f57d33b29b58d0dbe10b3

nova/compute/utils.py

@@ -37,7 +37,7 @@ def notify_usage_exists(instance_ref, current_period=False):
 
         Generates usage for last completed period, unless 'current_period'
         is True."""
-    admin_context = context.get_admin_context()
+    admin_context = context.get_admin_context(read_deleted='yes')
     begin, end = utils.current_audit_period()
     bw = {}
     if current_period:

nova/db/sqlalchemy/api.py

@@ -1610,7 +1610,9 @@ def instance_get_active_by_window_joined(context, begin, end=None,
     session = get_session()
     query = session.query(models.Instance)
 
-    query = query.options(joinedload('security_groups')).\
+    query = query.options(joinedload('info_cache')).\
+                  options(joinedload('security_groups')).\
+                  options(joinedload('metadata')).\
                   options(joinedload('instance_type')).\
                   filter(or_(models.Instance.terminated_at == None,
                              models.Instance.terminated_at > begin))