ceph-authtool: exit(1) when printing a non-existing key

ceph-authtool: exit(1) when printing a non-existing key

When printing a non-existing key, ceph-authtool exits with a success
value:

[root@ip-172-31-3-178 ~]# ceph-authtool /etc/ceph/ceph.mon.keyring -p -n
client.doesntexist ; echo $?
entity client.doesntexist not found
0

Expected result: 1

Signed-off-by: Gerhard Muntingh <gerhard@qux.nl>