Comment 9 for bug 1590278

Reviewed: https://review.opencontrail.org/21023
Committed: http://github.org/Juniper/contrail-controller/commit/bec7bf8fd1c581ba9abfba136ec8557b1bb05756
Submitter: Zuul
Branch: R3.0

commit bec7bf8fd1c581ba9abfba136ec8557b1bb05756
Author: Sachin Bansal <email address hidden>
Date: Wed Jun 8 11:38:52 2016 -0700

Add check for left and right vn

left or right vn of a service chain could have been deleted while
schema transformer was down. When it comes back up, it tries to
read these networks. We should add a check for None before accessing
these networks to avoid generating a traceback.

Change-Id: If2d3ffccdc912eaa64a84e17233a2fb3e3a84477
Closes-Bug: 1590278