Add tests to cover trunks

This patch set adds tests to cver the neutron trunks API [0].
Test lists, gets, creates, updates, and deletes trunks.
Part of "Increase Neutron RBAC Coverage" initiative [1]

[0] https://developer.openstack.org/api-ref/network/v2/index.html#trunk-networking
[1] https://storyboard.openstack.org/#!/story/2002641

Story: 2002641
Task: 22326
Change-Id: Ie59f02f5ecc1d04a16fb178444f231e4791e2079
2 files changed