vpnservice's router must have gateway interface set

[yong sheng gong]

at line
https://github.com/openstack/neutron/blob/master/neutron/services/vpn/service_drivers/ipsec.py#L172

it is obvious the router must have gateway interface set then it can be used as vpnservce router.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/60653

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/60756

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/60653
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=3e263ba6c58c43f71c02417f8948300e8cb5c462
Submitter: Jenkins
Branch: master

commit 3e263ba6c58c43f71c02417f8948300e8cb5c462
Author: Yong Sheng Gong <email address hidden>
Date: Sat Dec 7 16:59:18 2013 +0800

    validate if the router has external gateway interface set

    If the router wants to work with vpn service, we must
    make sure external gateway interface is set.

    This patch cannot prevent user from clearing the gateway interface
    of the router after the vpnservice is created.

    Change-Id: If0f00def949b31c1e3da7a2cd055454567201e4c
    Closes-Bug: #1258379