Fix issue with ceph-client relation handling

A bug was introduced when changing ceph-client to
an operator framework library that caused the
fallback application_name handling to present
a class name rather than a remote applicaiton name.

This change updates the handling to get at an
`app.name` rather than an `app`.

As a drive-by, this also allow-lists the fully-
qualified rename.sh.

Closes-Bug: #1995086
Change-Id: I57b685cb78ba5c4930eb0fa73d7ef09d39d73743
func-test-pr: https://github.com/openstack-charmers/zaza-openstack-tests/pull/1022

src/ceph_client.py

@@ -93,7 +93,7 @@ class CephClientProvides(Object):
         """Retrieve client application name from relation data."""
         return relation.data[unit].get(
             'application-name',
-            relation.app)
+            relation.app.name)
 
     def _handle_client_relation(self, relation, unit):
         """Handle broker request and set the relation data

tox.ini

@@ -27,7 +27,7 @@ install_command =
 commands = stestr run --slowest {posargs}
 allowlist_externals =
     charmcraft
-    rename.sh
+    {toxinidir}/rename.sh
 passenv =
     HOME
     TERM