Comment 7 for bug 1716573

Reviewed: https://review.opencontrail.org/35598
Committed: http://github.com/Juniper/contrail-controller/commit/061e29144039203fbddb526df962c7dcc936baa2
Submitter: Zuul (<email address hidden>)
Branch: master

commit 061e29144039203fbddb526df962c7dcc936baa2
Author: Suresh Venkata <email address hidden>
Date: Wed Sep 13 15:52:30 2017 -0700

Sanity bug fixes in cassandra cache and keystone authentication

Description: This commit has two fixes.

1) For calls made through api-lib, exclude_back_refs is true,
id_perms timestamp is used to cassandra cache has to be refresshed.
update_latest_col_ts doesn't update id_perms timestamp, when
symmetric refs are updated. Changed to call update_last_modified
does update id_perms timestamp as well as latest_col_ts.

2) keystone authentication when failed in neutron plugin code,
will return empty auth_hdrs. Because empty auth_hdrs are returned,
HTTP_X_ROLES were missing when the execution comes to RBAC.
When authentiation fails, auth headers are set to None, and this
will raise AuthFailed exception in plugin code, which client may
use to retry with a valid token.

Change-Id: I46827370bba90bbad1b36843474f636e3cf72f77
Closes-Bug: #1716311
Closes-Bug: #1716573