Add query for bug 1268274

The actual KeyError should be fixed with this Tempest change:

https://review.openstack.org/#/c/75610/

And the underlying nova/neutron bug is probably related to the
info_cache race issues that are already being worked for Icehouse.

This query is to fingerprint the existing KeyError failures and make
sure they are classified.

Related-Bug: #1268274

Change-Id: Ida32475f68d480dd62701b3a17068ca6d3b82aaa
Merge "Add query for bug 1268274"