Replacing ceph by ceph-mon leaves old ceph IP in /etc/ceph/ceph.conf

Environment:
* trusty-mitaka using latest charmstore revs
* single cinder unit, with "vip" set and related to hacluster
* single ceph unit, with no osd devices

When I run the following steps, taken from [1]:
"""
juju deploy --config no-bootstrap=True cs:trusty/ceph-mon
juju add-unit -n2 ceph-mon
# wait until ceph-mon units settle
juju add-relation ceph ceph-mon
# wait until units settle
juju add-relation ceph-mon ceph-osd
# wait until units settle
juju add-relation ceph-mon cinder
juju add-relation ceph-mon glance
juju add-relation ceph-mon nova-compute

# wait until units settle
juju remove-application ceph
"""

When I check glance's /etc/ceph/ceph.conf, new mon IPs are configured. However, cinder unit has the old IP and I needed to fix it by running:
juju run --unit cinder/0 hooks/config-changed

1. http://git.openstack.org/cgit/openstack/charm-deployment-guide/tree/deploy-guide/source/app-ceph-migration.rst