bgp-speaker without associating with router is not supported.

[Kengo Hobo]

Currently, MidoNet does not support bgp-speaker without associating with router.

To accomplish following purposes, it is necessary for MidoNet to support use case above
* Support BGP operation from neutron for MidoNet EdgeRouter.
* Unify behaviors in upstream and MidoNet.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/320434

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/320434
Committed: https://git.openstack.org/cgit/openstack/networking-midonet/commit/?id=77ce4048a53d77f9a766705057909a345afc9746
Submitter: Jenkins
Branch: master

commit 77ce4048a53d77f9a766705057909a345afc9746
Author: hobo.kengo <email address hidden>
Date: Tue May 24 10:42:58 2016 +0000

    BGP extension implementation(2nd stage)

    This patch includes following modifications.
    * support creation of bgp speaker without specifying router.
    * support gateway network operation for bgp speaker.

    Change-Id: Ifdce2cdc4df524ec23e885e4a10e70e4209049cb
    Closes-Bug: #1584645