auth,mon: don't log "unable to find a keyring" error when key is given

auth,mon: don't log "unable to find a keyring" error when key is given

This error is logged even if --key or --keyring are specified and
confuses users because the command actually does its job and exits
with success.  This primarily affects "rbd mirror pool peer bootstrap
import" command and rbd-mirror and cephfs-mirror daemons which connect
to the remote cluster with just mon_host and key:

  $ rbd mirror pool peer bootstrap import mypool tokenfile
  ... -1 auth: unable to find a keyring on /etc/ceph/..keyring,/etc/ceph/.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin,: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/..keyring,/etc/ceph/.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin,: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/..keyring,/etc/ceph/.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin,: (2) No such file or directory

Local cluster commands are affected too:

  $ rados --no-config-file --mon-host $MON_HOST --key $KEY lspools
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  ... -1 auth: unable to find a keyring on /etc/ceph/ceph.client.admin.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin: (2) No such file or directory
  device_health_metrics
  rbd

This was introduced in commit 98a2e5c59daa ("rados: translate errno to
str in CLI").

Fixes: https://tracker.ceph.com/issues/51628
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit 70aa026b097d919b41b2a1221d73b326557f75e3)