add code to concat keyring/user information to ceph.conf

Added code to ceph::key to add informations about the generated keys
to the ceph.conf. This should make it easier in some cases to access
keyring information for the user/client in some cases.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
(cherry picked from commit 9d140f2f0c467b5e2416c822bf67d06c80b85234)