taas agent should be an agent extension

[YAMAMOTO Takashi]

taas agent fails if it's run before ovs-agent creates br-tun.
probably it should be an agent extension driver.

http://docs.openstack.org/developer/neutron/devref/l2_agent_extensions.html

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/247948

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/243992
Committed: https://git.openstack.org/cgit/openstack/tap-as-a-service/commit/?id=5e6a3a9b34661a6e054d4d91530ac2718c6ffdde
Submitter: Jenkins
Branch: master

commit 5e6a3a9b34661a6e054d4d91530ac2718c6ffdde
Author: YAMAMOTO Takashi <email address hidden>
Date: Wed Nov 11 12:40:02 2015 +0900

    Add devstack plugin

    Closes-Bug: #1501795
    Related-Bug: #1515104
    Change-Id: Ia1c266db46ecbced7fe1661ee7df464fa3c4e90d

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/247948
Committed: https://git.openstack.org/cgit/openstack/tap-as-a-service/commit/?id=b402dc4d9c98e2ab7d51ed267516569db649e7f3
Submitter: Jenkins
Branch: master

commit b402dc4d9c98e2ab7d51ed267516569db649e7f3
Author: YAMAMOTO Takashi <email address hidden>
Date: Fri Nov 20 15:49:37 2015 +0900

    Add a minimum documentation for devstack plugin

    Related-Bug: #1501795
    Related-Bug: #1515104
    Change-Id: Id2d37be361b6e675620604abff15e16fa09378b1

[YAMAMOTO Takashi (yamamoto)]

https://review.openstack.org/#/c/480031/