ceph_key: handle error in a better way

ceph_key: handle error in a better way

When calling the `ceph_key` module with `state: info`, if the ceph
command called fails, the actual error is hidden by the module which
makes it pretty difficult to troubleshoot.

The current code always states that if rc is not equal to 0 the keyring
doesn't exist.

`state: info` should always return the actual rc, stdout and stderr.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1964889
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>