Make cephadm_key module stateless

This module should never write to files because they
always exist inside the cephadm container, which
is ephemeral. Remove all file-writing functions and
references to keyrings.

Author: m-bull

CHANGELOG.rst

@@ -4,6 +4,26 @@ stackhpc.cephadm Release Notes
 
 .. contents:: Topics
 
+v1.16.0
+=======
+
+Release Summary
+---------------
+
+Fix idempotency issue in cephadm_keys plugin. `cephadm_keys` no
+longer generates keyring files on Ceph hosts, and additional tasks
+are required to write keyring files to disk - see the cephadm_keys
+README.md for further details.
+
+
+Minor Changes
+-------------
+
+- Deprecate `generate_keys` functionality in cephadm_keys plugin
+- Deprecate `fetch_inital_keys` functionality in cephadm_keys plugin
+- Fix issue with idempotency in cephadm_keys plugin, by no longer
+  generating user keyring files on Ceph hosts.
+
 
 v1.13.0
 =======