Add advsvc role to neutron policy file

[OpenStack Infra]

https://review.openstack.org/101281
commit d4f00659eb18c6a5df2ce6d35202b0a4a9409f70
Author: Kyle Mestery <email address hidden>
Date: Wed Jun 18 11:04:52 2014 +0000

    Add advsvc role to neutron policy file

    Add in a default "advsvc" user and the logic in the Neutron policy
    infrastructure which will allow this user to create/get/update/delete
    ports on other tenants networks, as well as view other tenants
    networks. This is for the use case of letting advanced services have
    a user to put ports on other tenants networks. By default, we do not
    define any roles for the policy "context_is_advsvc", but rely on
    operators to specify the likely value of "role advsvc".

    DocImpact

    Closes-Bug: #1331836

    Change-Id: I94cb3383eb1fed793934719603f888dbbdbbd85a
    Co-Authored-By: Susanne Balle <email address hidden>

[venkatamahesh (venkatamaheshkotha)]

This is updated at : https://github.com/openstack/openstack-manuals/blob/master/doc/config-reference/source/networking/sample-configuration-files.rst#policyjson