Resync the latest charms.ceph to avoid direct installation
of Python 2 modules which are not available in the latest
Ceph packaging which no longer provides Python 2 support.
This commit also updates two action which still used Python
to use Python 3 (inline with the rest of the charm).
Change-Id: I8fc2a1aa17e48ef5dac9b9974c33b9620fcb7c70