juju units lose addressing, resulting in failed hook execution

[James Page]

Example:

https://openstack-ci-reports.ubuntu.com/artifacts/test_charm_pipeline_amulet_full/openstack/charm-ceph-osd/298412/7/2016-07-06_18-12-23/index.html

Symptomatically the deployment fails with a hook execution error; juju status reveals that the unit is in a problem state:

mysql/0 error idle 1.25.5 10 3306/tcp hook failed: "shared-db-relation-changed" for glance:shared-db

...

10 pending 1.25.5 a8a71066-18db-4d94-83ee-c0bb0de97635 trusty arch=amd64 cpu-cores=1 mem=1536M root-disk=10240M availability-zone=nova

[James Page (james-page)]

Juju bug 1577556