L3 agent making RPC calls to get external network id

[Carl Baldwin]

In _process_routers, the L3 agent makes an RPC call each time that _process_routers is called to get the external network id as long as it was not configured using the gateway_external_network_id configuration option.

This adds some time process a router. Since the external id will not be changing, we should be able to get away with fetching and saving this value once.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/66928

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/66928
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=702e1fbf7ad5dd961dfd35cd6a0e54d4d6da5e34
Submitter: Jenkins
Branch: master

commit 702e1fbf7ad5dd961dfd35cd6a0e54d4d6da5e34
Author: Carl Baldwin <email address hidden>
Date: Wed Jan 15 18:46:17 2014 +0000

    L3 agent fetches the external network id once

    Rather than fetching the id of the external network each time that
    _process_routers is called, get it once and remember it. If the agent
    is ever requested to connect to a different ext-net then it will fetch
    the current ext-net to double check for the unlikely event that the
    ext-net has changed. If it has then it will remember the new ext-net.

    This is only applicable in the case where there is only one ext-net
    that has not been configured explicitly in the config file. That was
    the only case that would cause an RPC message in the first place.

    Change-Id: I40bbbf6233131ea5d40122ef9495fd3cb7dc823a
    Closes-Bug: #1269567