Comment 10 for bug 1812118

Reviewed: https://review.opendev.org/689853
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=8da6836b5b232c1847bb4dee78239e79c6ec7d5c
Submitter: Zuul
Branch: stable/train

commit 8da6836b5b232c1847bb4dee78239e79c6ec7d5c
Author: Brian Haley <email address hidden>
Date: Wed Jul 10 16:01:25 2019 -0400

    Use admin context when updating router gateway

    When a router gateway is updated and the subnet changes,
    we need to use the admin context in order for the operation
    to succeed. Since the target network has already been
    verified to be external, this is OK. The other operations
    in this area such as create and delete already do the
    same thing.

    Added a fullstack test that moves a gateway between subnets
    and verifies it's reachable afterwards.

    Change-Id: Iead87ba6182d633f0f808032166e02e767fcffae
    Closes-bug: #1812118
    (cherry picked from commit 040b550a861ce321c87ac33e92836a502d9531d3)