Comment 8 for bug 1691590

Reviewed: https://review.opencontrail.org/32643
Committed: http://github.com/Juniper/contrail-controller/commit/42eb794b6ce51b6d9034e9214b7f097451203709
Submitter: Zuul (<email address hidden>)
Branch: master

commit 42eb794b6ce51b6d9034e9214b7f097451203709
Author: Sahil <email address hidden>
Date: Wed Jun 7 15:47:53 2017 -0700

[api_server]: Fix to call ref_update function.

1. Added a call to ref_update function in _put_common().
We were only doing dbe_update at the time of ref_update_http_post.

2. Modified update_last_modified function for cassandra so that it
doesn't throw a traceback when obj. gets deleted at the time
of obj. update

Change-Id: I36064a8b07503732ed76a4ffaddef9ef02a3c054
Closes-Bug: 1691590