generic_switch lacks functional tests

[Pavlo Shchelokovskyy]

We should implement at least basic functional tests.

Idea: create an 'exercise.sh' script in devstack plugin and run it on a minimal gate that has keystone, neutron and our plugin installed.
The script should:
- create a port in Neutron
- update its fields (link_local_info etc)
- check with direct OVS commands that corresponding changes propagated to OVS and were applied.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/294058

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/294058
Committed: https://git.openstack.org/cgit/openstack/networking-generic-switch/commit/?id=47330e9eb3a41dda8dda835ef2e974cdf03d8dd9
Submitter: Jenkins
Branch: master

commit 47330e9eb3a41dda8dda835ef2e974cdf03d8dd9
Author: Pavlo Shchelokovskyy <email address hidden>
Date: Wed Mar 16 18:34:19 2016 +0200

    Add functional test

    - creates new OVS bridge and adds port
    - create Neutron port
    - update Neutron port with proper `link_local_information`
    - check that requested changes have propagated to OVS
    - delete dridge

    As setting some Neutron port properties is not available from Neutron
    CLI, this test uses a mixture of BASH (for OVS query and manipulation)
    and Python (for Neutron API interactions).

    Change-Id: I335b8af77c036be6bba4506c675e6e1f10f26097
    Closes-Bug: #1557355