Implement L2GW for MidoNet L2GW

[Ryu Ishimoto]

Update the current L2GW extension support to work with midonet's L2GW implementation.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/302150

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/306343

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/308169

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/302150
Committed: https://git.openstack.org/cgit/openstack/networking-midonet/commit/?id=79560ed935a4182d372eb3060a1a52318296fb12
Submitter: Jenkins
Branch: master

commit 79560ed935a4182d372eb3060a1a52318296fb12
Author: Hiroyuki Ito <email address hidden>
Date: Wed Apr 6 07:52:00 2016 +0000

    Add a constraint on gateway device model

    Before adding a model for network vlan gateway which is similar
    to existing GatewayOverlayRouterDevice model, make the role of the
    existing model clear with this refactoring.

    Change-Id: I254485e2bdd241192289d5c9148b3ce1eca2fa3f
    Related-Bug: #1554965

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/306343
Committed: https://git.openstack.org/cgit/openstack/networking-midonet/commit/?id=4868a728afad6b850621ee47f57c8e6f741973bc
Submitter: Jenkins
Branch: master

commit 4868a728afad6b850621ee47f57c8e6f741973bc
Author: Hiroyuki Ito <email address hidden>
Date: Wed Apr 6 06:47:32 2016 +0000

    Support gateway device of network_vlan type

    MidoNet supports gateway device of network_vlan type as well.
    This patch includes the following:

      * Extend Midonet Gateway Device Management Service plugin
      * Add unit tests for gateway device of network vlan type

    Partial-Bug: #1554965
    Change-Id: I4b57dd4c63f87ca9a9f5ddaded6866cbdb434287

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/308169
Committed: https://git.openstack.org/cgit/openstack/networking-midonet/commit/?id=d9b63d06ca18ae81b45564169bcd5d3b66890cf5
Submitter: Jenkins
Branch: master

commit d9b63d06ca18ae81b45564169bcd5d3b66890cf5
Author: Hiroyuki Ito <email address hidden>
Date: Mon Apr 18 10:27:25 2016 +0000

    Support L2GW with network_vlan gateway device

    Support l2 gateway with gateway device of network_vlan type.
    This patch includes the following:

      * Select segmentation_id validation from that of vxlan and vlan
        according to gateway device type
      * Add unit tests for above change
      * Add basic unit tests for l2 gateway using gateway device with
        network_vlan type

    Closes-Bug: #1554965
    Change-Id: If8fb314897c4c2af7f5263bc1d28e334626fe0ac