Config for "region" not propagated to all relations

[Peter Sabaini]

When setting the "region" config in n-c-c, the region setting doesn't
get updated everywhere (eg. not in neutron-gateway)

The quantum-network-service relation should carry the region data, but
the config-changed hook doesn't update units via this relation.

Eg., we've set region to 'EU' but the relation still has:

juju run --unit neutron-gateway/0 'relation-get -r quantum-network-service:60 - nova-cloud-controller/0'
...
region: bootstack-staging
...

This is from n-c-c revno=163, but afaict from the config_changed() source this should apply to revno=171 as well

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/428118

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/428118
Committed: https://git.openstack.org/cgit/openstack/charm-nova-cloud-controller/commit/?id=ad6fbd48db1797e1cfe201e158331edef205a1f1
Submitter: Jenkins
Branch: master

commit ad6fbd48db1797e1cfe201e158331edef205a1f1
Author: James Page <email address hidden>
Date: Thu Feb 2 12:42:07 2017 +0000

    Ensure configuration changes propagated fully

    nova-cloud-controller provides its region setting to the nova
    services hosted in neutron-gateway units; ensure that any changes
    to configuration are correctly propagated to related units.

    Change-Id: Iea002d4379339abf64742409e36d237b163420c5
    Closes-Bug: 1513411